Category: CBSE

Here are the detailed Wave Optics Class 12 Notes Chapter 10. Thus the notes will be very helpful in preparation for examinations. Class 12 Physics notes cover all the important topics that are listed. It gives students a basic understanding of the past and the development of laws in physics. https://meritbatch.com/wave-optics-cbse-notes-class-12-physics/

Wave Optics Class 12 Notes Chapter 10

Wave Optics Class 12 Notes
1. Wave Optics Describes the connection between waves and rays of light. According to wave theory of light, light is a form of energy which travels through a medium in the form of transverse wave.
2. Wave front The locus of all those particles which are vibrating in the same phase at any instant is called wave front. Thus, wave front is a surface having same phase of vibrating particles at any instant at every point on it.
Chapter 10 Physics Class 12 Notes
3. Phase Speed Phase speed is the speed with which wave front moves and it is equal to wave speed.
4. The shape of wavefront due to a
(i) point source is spherical
(ii) line source is cylindrical
(iii) source at infinity is a plane.
Wave Optics Class 12
5. A line perpendicular to a wave front is called a ray. The direction of rays are always perpendicular to the wave front along the direction of propagation of wave.
Ch 10 Physics Class 12 Notes
6. Huygens’ Principle Huygens’ principle is essentially a geometrical construction, which gives the shape of the wave front at any time, allows us to determine the shape of the wave front at a later time. According to Huygens’ principle,
(i) Every point on a wave front behaves like a light source and emits secondary wavelets.
(ii) The secondary wavelets spread in all directions in space (vacuum) with the velocity of light.
(iii) The envelope of wave front of secondary wavelets, after a given time, along forward direction gives the new position of wave front.
7. The laws of reflection and refraction can be verified using Huygens’ wave theory.
Wave Optics Notes
8. Huygens’ wave theory successfully explains the phenomenon of interference, diffraction and polarisation.
9. As, frequency v is characteristic of the source, therefore v = 1/T remains the same as light travels from one medium to another.
10. Wavelength is inversely proportional to refractive index (μ) of the medium
i.e. λ’ = λ/μ
11. Behaviour of a Prism, Lens and Spherical Mirror towards Plane Wave front

Class 12 Wave Optics Notes
12. Laws of reflection on the basis of Huygens’ wave theory As shown in figure, consider a plane wave front AB incident on the reflecting surface XY, both the wave front and the reflecting surface being perpendicular to the plane of paper.

First the wave front touches the reflecting surface at B and then at the successive points towards C. In accordance with Huygens’ principle, from each point on BC, secondary wavelets start growing with the speed c. During the time the disturbance from A reaches the point C the secondary wavelets from B must have spread over a hemisphere of radius BD = AC = ct, where t is the time taken by the disturbance to travel from A to C. The tangent plane CD drawn from the point C over this hemisphere of radius ct will be the new reflected wave front.
Let angles of incidence and reflection be i and r, respectively . In AABC and ADCB, we have

i.e. the angle of incidence is equal to the angle of reflection. The proves the first law of reflection.
Further, since the incident ray SB, the normal BN and the reflected ray BD are respectively perpendicular to the incident wave front AB, the reflecting surface XY and the reflected wave front CD (all of which are perpendicular to the plane of the paper) therefore, they all lie in the plane of the paper i.e. in the same plane. This proves the second law of reflection.
Class 12 Physics Wave Optics Notes
13. Law of refraction on this basis of Huygens’ wave theory Consider a plane wavefront AB incident on a plane surface XY, separating two media 1 and 2, as shown in Figure.
Let v₁ and v₂ be the velocities of light in two media, with v₁ <v₂.

The wave front first strikes at point A and then at the successive points towards C. According to Huygens’ principle, from each point on AC, the secondary wavelets starts growing in the second medium with speed v₂. Let the disturbance take time t to travel from B to C, then BC = v₁t. During the time the disturbance from B reaches the point C, the secondary wavelets from point A must have spread over a hemisphere of radius AD = v₂t in the second medium. The tangent plane CD drawn from point C over this hemisphere of radius v₂t will be the new refracted wave front.
Let the angles of incidence and refraction be i and r, respectively.
From right AABC, we have


This proves Snell’s law of refraction. The constant ¹μ₂ is called the refractive index of the socond medium with respect to first medium.
Further, since the incident ray SA, the normal AN and the refracted ray AD are respectively perpendicular to the indicent wave front AB, the dividing surface XY and the refracted wave front CD (all perpendicular to the plane of the paper), therefore, they all lie in the plane of the paper, i.e. in the same plane. This proves another law of refraction.

CBSE Notes

Here are the detailed Ray Optics and Optical Instruments Class 12 Notes Chapter 9. Thus the notes will be very helpful in preparation for examinations. Class 12 Physics notes cover all the important topics that are listed. It gives students a basic understanding of the past and the development of laws in physics. https://meritbatch.com/ray-optics-optical-instruments-cbse-notes-class-12-physics/

Ray Optics and Optical Instruments Class 12 Notes Chapter 9

Ray Optics Class 12 Notes
1. Ray Optics or Geometrical Optics In this optics, the light is considered as a ray which travels in a straight line. It states that for each and every object, there is an image.
Ray Optics Class 12
2. Reflection Reflection is the phenomenon of changing the path of light without any change in the medium.
Ray Optics Notes
3. Reflection of Light The returning back of light in the same medium from which it has come after striking a surface is called reflection of light.
Optics Class 12 Notes
4. Laws of Reflection
Two laws of reflection are given as below:
(i) The angle of incidence i is equal to the angle of reflection r.
i.e. ∠i = ∠r.
(ii) The incident ray, reflected ray and normal to the reflecting surface at the point of incidence all lie in the same plane.

5. Total number of images formed by two plane mirrors inclined at an angle θ with each other is given by

6. Reflecting surface of a spherical mirror is a part of a hollow sphere. Spherical mirrors are of two types, (i) Concave spherical mirror (ii) Convex spherical mirror.

7. Sign Convention All measurements should be taken from pole of mirror. All measurements along the direction of incident ray will be positive and opposite to incident ray are negative. All the measurements for the distances above the principal axis are taken as positive and below the principal axis are taken as negative.
8. For a real object, u is negative whereas v is negative for real image and positive for virtual image.
Class 12 Physics Ray Optics Notes
9. Mirror Formula Mirror formula is a relation between focal length of the mirror and distances of objects and image from the mirror.

11. Linear Magnification The ratio of the size of the image formed by a spherical mirror I to the size of the object O is called the linear magnification produced by the spherical mirror.

12. Magnification (m) It is negative corresponding to real image and positive for virtual image.
Optical Instruments Class 12
13. Refraction The phenomenon of changing in the path of light as it goes from one medium to another is called refraction.
14. Laws of Refraction

Two laws of refraction are given as below:
(i) The incident ray, refracted ray and the normal to the refracting surface at the point of incidence lie in the same plane.
(ii) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for the two given media. This constant is denoted by n and is called the relative refractive index.
n = sin i/sin r (Snell’s law)
where, n is refractive index of the second medium when first medium is air.

17. Total Internal Reflection (TIR) When a ray of light travelling from denser medium to rarer medium is incident at the interface of two medium at an angle greater than the critical angle for the two media, the ray is totally reflected back to denser medium. This phenomenon is called Total Internal Reflection. It occurs only when angle of incidence in denser medium is greater (not equal) than critical angle, i.e. i> i_c.

Ray Optics Notes Class 12
18. Principle of reversibility of light states that when final path of a ray of light after any number of reflections and refractions is reversed, the ray retraces its entire path.


22. Optical fibre, mirage, sparkling of diamond, totally reflecting prism, etc. work on the principle of total internal reflection.

24. Lens is a transparent medium bounded by two surfaces of which one or both surfaces are spherical.
(i) Convex or Converging Lens A lens which is thicker at the centre and thinner at its end is called convex lens.
Convex lenses are of three types which are given as below:

(ii) Concave or Diverging Lens A lens which is thinner at the centre and thicker at its ends is called a concave lens.
Concave lenses are of three types which are given as below:

Class 12 Optics Notes
25. Lens maker’s formula

26. When lens of refractive index μ is immersed in a medium of refractive index μ, then
(i) When lens is taken in another medium, then focal length changes to f_m which is given by


28. Power of Lens The ability of a lens to converge or diverge the rays of light incident on it is called the power of the lens.

29. Power of combination lenses in contact is given by

30. Magnification by combination of lenses
m = m₁ × m₂ × m₃ ………..
31. (i) Prism have got the property of bending the incident light towards its base.
A prism is a portion of a transparent medium bounded by two plane faces inclined to each other at a suitable angle.

(ii) When the prism is adjusted at angle of minimum deviation, then
(a) angle of incidence is equal to the angle of emergence

31. Dispersion by a Prism The phenomenon of splitting of light into its component colours is known as dispersion.
Angular Dispersion Angular dispersion produced by a prism for white light is the difference in the angles of deviation for two extreme colours i.e. violet and red.


Dispersive Power Dispersive power of a prism is defined as the ratio of angular dispersion to the mean deviation produced by the prism.

33. Combining two thin prisms we can study two conditions

CBSE Notes

Here are the detailed Electromagnetic Waves Class 12 Notes Chapter 8. Thus the notes will be very helpful in preparation for examinations. Class 12 Physics notes cover all the important topics that are listed. It gives students a basic understanding of the past and the development of laws in physics. https://meritbatch.com/electromagnetic-waves-cbse-notes-class-12-physics/

Electromagnetic Waves Class 12 Notes Chapter 8

Electromagnetic Waves Class 12 Notes
1. Displacement Current The current which comes into play m the region in which the electric field and the electric flux is changing with time. It is given by

Electromagnetic Waves Class 12
2. Need for Displacement Current Ampere’s circuital law for conduction current during charging of a capacitor was found inconsistent. Therefore, Maxwell modified Ampere’s circuital law.
3. The displacement current produces in space due to change of electric flux linked with the surface. This reveals that, varying electric field is the source of magnetic field.
Electromagnetic Waves Notes
4. Maxwell’s Equations of Electromagnetic Waves Maxwell’s equations are the basic laws of electricity and magnetism. These equations give complete description of ail electromagnetic interactions.
There are four Maxwell’s equations which are explained below:

Em Waves Class 12 Notes
5. Electromagnetic Waves An electromagnetic wave is a wave radiated by an accelerated or oscillatory charge in which varying magnetic field is the source of electric field and varying electric field is the source of magnetic field. Thus two fields becomes source of each other and the wave propagates in a direction perpendicular to both the fields.
Em Waves Class 12
6. Electromagnetic waves are transverse in nature, i.e. electric and magnetic fields are perpendicular to each other and to the direction of wave propagation. Electromagnetic waves are not. deflected by electric and magnetic fields.

7. E (electric field) and B (magnetic field) in electromagnetic waves are in same phase.
Class 12 Physics Chapter 8 Notes
8. Speed of electromagnetic wave

9. The energy in electromagnetic wave is divided on average equally between electric and magnetic fields.
Em Waves Notes

11. Linear momentum delivered to the surface, p= U/c
where, U = total energy transmitted by electromagnetic waves and c = speed of electromagnetic wave.
Class 12 Electromagnetic Waves Notes
12. Electromagnetic Spectrum The systematic sequential distribution of electromagnetic waves in ascending or descending order of frequency or wavelength is known as electromagnetic spectrum. The range varies from 10^-12 m, to 10⁴ m, i.e. from γ-rays to radio waves.

13. Elementary facts about the uses of electromagnetic waves
Radio waves
(i) In radio and TV communication.
(ii) In astronomical field.
Microwaves
(i) In RADAR communication.
(ii) In analysis of molecular and atomic structure.
(iii) For cooking purpose.
Class 12 Physics Electromagnetic Waves Notes
Infrared waves
(i) In knowing molecular structure. (ii) In remote control of TV VCR, etc.
Ultraviolet rays
(i) Used in burglar alarm. (ii ) To kill germs in minerals.
X-rays
(i) In medical diagnosis as they pass through the muscles not through the bones.
(ii) In detecting faults, cracks, etc., in metal products,
γ-rays
(i) As food preservation. (ii) In radiotherapy.
Electromagnetic Waves Notes Class 12
14. The optical effect is produced by electric field vector of the electromagnetic waves.

CBSE Notes

CBSE Class 7 Science Notes Chapter 18 Waste Water Story Pdf free download is part of Class 7 Science Notes for Quick Revision. Here we have given NCERT Class 7 Science Notes Chapter 18 Waste Water Story. https://meritbatch.com/waste-water-story-class-7-notes/

CBSE Class 7 Science Notes Chapter 18 Waste Water Story

Waste Water Story Class 7 Notes
Water is an elixir of life. We all use water and in that process of using, we make it dirty. The water rich in a lather, mixed with oil and other pollutants that go down the drains from sinks, showers, toilets, laundries is dirty. It is called wastewater.

We use water every day for drinking, bathing, washing clothes, cooking food, washing utensils, flushing toilets, mopping the floors, etc. We cannot think of our life without water. We use lots of water daily which is passed on to the drainage system every day.

Water, Our Lifeline
Water is needed by all forms of life. Clean water is a basic need of human beings. Unfortunately, clean water is not available to a large segment of human populations.

The water which is unfit for human consumption becomes the source of many water-borne diseases which ultimately lead to loss ( of human life. It is estimated that one billion human beings do not get safe drinking water. So, realising the urgency we celebrate 22nd March as World Water Day to bring awareness amongst people for safe water, fit for human consumption.
Thus, the water is cleaned by removing pollutants before it enters a waterbody or is reused. This process of wastewater treatment is commonly known as sewage treatment which takes place in several steps as discussed later.

On the World Water Day, i.e. 22 March 2005, the General Assembly of the United Nations proclaimed the period 2005-2015 as the International Decade for action on Water for Life. All efforts made during this decade aim to reduce by half the number of people who do not have access to safe drinking water.

Wastewater Story Class 7 Notes
Sewage
It is wastewater released by homes, industries agricultural fields and other human activities. It also includes rainwater that has run down the street during a storm or heavy rain and it is liquid waste. Most of its water has dissolved and suspended impurities called contaminants.

Composition of Sewage
The following components make the sewage:

• The organic impurities present in sewage are human faeces, animal wastes (like animal dung), urea (as urine), oil, fruits and vegetable wastes, pesticides, herbicides, etc.
• The inorganic impurities present in sewage are nitrates, phosphates and metals.
• The nutrients present in sewage are nitrogen and phosphorus.
• The bacteria present in sewage include those bacteria which cause water-borne diseases such as cholera and typhoid.
• The other microbes present in sewage are Protozoa which cause a water-borne disease called dysentery.

Water Freshens Up: An Eventful Journey
In a house (a public building) generally, there are two sets of pipes, i.e. one set of pipes brings clean drinking water into the house and the other set of pipes takes away wastewater (sewage) from houses. For proper sanitation, a well-maintained sewage system is required.

Sewerage System
The pipes which carry away wastewater or sewage from houses and other buildings are buried under the ground. An underground pipe which carries away dirty drainage water and waste matter is called sewer. The provision of drainage at a place by laying sewers under the ground is called sewerage. Actually, sewerage is an underground network of interconnected pipes called sewers that carries the sewage from the place where it is produced to the sewage treatment plants, where it is processed.

Class 7 Science Chapter 18 Notes
Manholes
A manhole is a covered vertical hole in the ground, pavement or road, above the underground sewer pipeline through which a worker can go down up to the sewer pipes for inspection, cleaning, etc. Manholes are provided at every 50-60 m distance in the main sewer pipeline. Manholes are also provided at the junction of two or more sewers and at points where there is a change in the direction of the sewer line.

Treatment of Polluted Water
Perform the following activity. It will help you to understand the processes that take place at the wastewater treatment plant.

Wastewater Treatment Plant (WWTP)
A place where wastewater or sewage from houses and other buildings is brought for processing is called wastewater treatment plant.
Treatment of wastewater involves physical, biological and chemical processes depending on the nature of contaminants.

Class 7 Science Ch 18 Notes
1. Physical Process (Screening)
The bar screens first remove the large rubbish objects like rags, sticks, cans, polybags, napkins, sanitary towels, etc., from the wastewater.

After passing through the bar screen, wastewater is taken to a tank called grit and sand removal tanks. In this, sand and grit settle down slowly at the bottom of the tank as water passes slowly through this tank. The settled sand and impurities are removed from the tanks from time to time.

Ncert Class 7 Science Chapter 18 Notes
2. Biological Process
The first sedimentation tank is sloped towards the centre. Solid like faeces settle at the bottom and is called sludge which is removed by a scraper. Oils and grease float at the surface of the water are removed by a skimmer. The biogas produced (by anaerobic bacteria) in the process can be used as fuel or can be used to produce electricity. Here, water gets cleared of rubbage, oil, grease, etc and we get clarified water which is sent to aeration tank now. In the aeration tank, the watery waste already contains bacteria (aerobic) in it. The compressed air bubbles are passed through this waste to provide 02 to the bacteria to increase bacterial activity which ultimately digests human waste, food waste, soaps and other unwanted and harmful matter still remaining in the wastewater leaving behind fairly pure water.

Ch 18 Science Class 7 Notes
3. Chemical Process
The water after aeration tank is allowed to stand in a second sedimentation tank. Here, the microbes present get settled at the bottom at the tank in the form of activated sludge which is about 97% water. At this stage, water has very low level of organic matter suspended matter and does not contain many harmful things. It is safe for human consumption but is disinfected by chlorine or ozone before distributing it.

Waste Water Story Class 7 Notes Pdf
Become an Active Citizen
Waste generation is a natural part of human activity but we can limit the type of waste and quantity of waste produced. Often we have been repelled by an offensive smell. The sight of open drains is disgusting. The situation worsens in the rainy season when the drains start overflowing. We have to wade through the mud pools on the roads. Most unhygienic and unsanitary conditions prevail. Flies, mosquitoes and other insects breed in it.

We should be an enlightened citizen and approach the municipality or the gram panchayat. We should also insist that open drains should be covered. If the sewage of any particular house makes the neighbourhood dirty. We should request them to be more considerate about other’s health.

Note: We should plant Eucalyptus trees all along sewage ponds. These trees absorb all surplus wastewater rapidly and release pure water vapour into the atmosphere.

Better House Keeping Practices
We must minimise and manage waste at our houses before its disposal in the following manner:

• Cooking oil and fats should not be thrown down the drain. They can harden and block the pipes. In an open drain, the fats clog the soil pores reducing its effectiveness in filtering water. Throw oil and fats in the dustbin.
• Used tea leaves, solid food remains, soft toys, cotton, sanitary towels, etc., should also be thrown in the
  dustbin. These wastes choke the drains. They do not allow the free flow of oxygen. This hampers the degradation process.
• The chemicals like paints, solvents, insecticides, medicines and motor oils should not be thrown in drains as they kill helpful microbes which digest the organic waste.

Class 7 Science Wastewater Story Notes
Sanitation and Disease
Contaminated water and poor sanitation practices are the major causes of the number of infectious diseases in our country. Safe sewage disposal facilities are still not available at many cities and villages in India. So, people go to open places and defecate. This causes the increase in insect-vector population which transmit diseases like cholera, typhoid, meningitis, etc.

Untreated human excreta is a health hazard which causes soil pollution and water pollution also. The river water and groundwater are sources of water for drinking for many people. So, the contaminated water can spread many diseases especially water-borne.

Vermi-processing Toilets
In the vermi-processing toilets, human excreta is treated by earthworms in a pit. The earthworms usually eat up all organic matter present in human excrete and turn it into compost. These are tow water use toilets for the safe processing of human.

Alternate Arrangement for Sewage Disposal
Low cost outside the sewage disposal system has been developed to take care of places where there is no sewage system, e.g. rural areas, isolated buildings. These are described below:
Class 7th Science Chapter 18 Notes
(i) Septic tanks: Septic tank is a low-cost onsite sewage disposal system. Septic tanks are suitable where there is no sewerage made. These tanks need cleaning every four to six months.

A septic tank usually consists of a big, covered underground tank made of concrete having an inlet pipe at one end and on outlet pipe at the other end. The toilet seat is connected to the inlet pipe of the septic tank. The human excreta from the toilet seat enters into the septic tank through the inlet pipe. The solid part of excreta keeps on collecting at the bottom of the septic tank in the form of a sludge whereas watery waste remains above it.

The anaerobic bacteria breakdown most of the solid organic matter present in human excreta due to which the volume of solid waste is reduced too much. The digested solid waste keeps on depositing at the bottom of septic tank. The watery waste is also cleaned by anaerobic bacteria. The excess water goes out of the septic tank through the outlet pipe and get absorbed in soil.

Class 7 Wastewater Story Notes
(ii) Composting pits: These are self-sustained human waste disposal units which is not connected to a sewer line or a septic tank. A composting toilet breaks down and dehydrates human waste to compost.

Wastewater Treatment Plant Class 7 Notes
(iii) Chemical toilets: These toilets have limited storage capacity for human waste and need to be emptied periodically. These are the toilets which use chemically treated reservoir located just below the toilet seats. The chemicals reduce the foul smell coming out of human excrete and carry out partial disinfection of human waste.

Sanitation at Public Places
In our country, fairs are organised periodically. A large number of people participate in them. In the same way, railway stations, bus depots, airports, hospitals are very busy places. Thousands of people visit them daily which generate large amount of waste. It must be disposed of properly otherwise epidemics could break out. The government has laid down certain standards of sanitation but unfortunately, they are not strictly enforced. We should not scatter litter anywhere. If there is no dustbin in sight, we should carry the litter at home and throw it in the dustbin.

Wastewater Story Notes
Conclusion
We all have a role to play in keeping our environment clean and healthy. We must realise our responsibility in maintaining the water sources in a healthy state. Adopting good sanitation practices should be our way of life. As an agent of change your individual initiative will make a great difference. Influence others with your energy ideas and optimum, A lot con be done if people work together. There is great power in collective action.
As an active citizen, we have many responsibilities regarding sanitation. These can be listed as follows:

• To ensure that our surroundings are clean.
• To ensure that the sewerage system in our house is properly managed.
• If any leakage or an open drain in the sewerage system is present, then it should be reported to the municipality or the gram panchayats to insist that the open drain must be covered properly and several air and water-borne diseases can be prevented.

Note: Mahatma Gandhi said, ‘No one needs to wait for anyone else to adopt a humane and enlightened course of action’.

We hope the given CBSE Class 7 Science Notes Chapter 18 Waste Water Story Pdf free download will help you. If you have any query regarding NCERT Class 7 Science Notes Chapter 18 Waste Water Story, drop a comment below and we will get back to you at the earliest.

Here are the detailed Electromagnetic Induction Class 12 Notes Chapter 6. Thus the notes will be very helpful in preparation for examinations. Class 12 Physics notes cover all the important topics that are listed. It gives students a basic understanding of the past and the development of laws in physics. https://meritbatch.com/electromagnetic-induction-cbse-notes-class-12-physics/

Electromagnetic Induction Class 12 Notes Chapter 6

Electromagnetic Induction Class 12
1. Magnetic Flux The magnetic flux linked with any surface is equal to total number of magnetic lines of force passing normally through it. It is a scalar quantity.

2. The phenomenon of generation of current or emf by changing the magnetic flux is known as Electromagnetic Induction EMI).
Electromagnetic Induction Notes
3. Faraday’s Law of Electromagnetic Induction
First Law Whenever magnetic flux linked with the closed loop or circuit changes, an emf induces in the loop or circuit which lasts so long as change in flux continuous.
Second Law The induced emf in a closed loop or circuit is directly proportional to the rate of change of magnetic flux linked with the closed loop or circuit

where, N = number of turns in loop.
Negative sign indicates the Lenz’s law.
4. Lenz’s Law The direction of induced emf or induced current is such that it always opposes the cause that produce it.
NOTE: Lenz’s law is a consequence of the law of conservation of energy.
Emi Class 12
5. If N is the number of turns and R is the resistance of a coil. The magnetic flux linked with its each turn changes by dФ in short time interval dt, then induced current flowing through the coil is

6. If induced current is produced in a coil rotated in a uniform magnetic field, then

7. Motional Emf The potential difference induced in a conductor of length l moving with velocity v, in a direction perpendicular to magnetic field B is given by

Chapter 6 Class 12 Physics Notes
8. Fleming’s Right Hand Rule If the thumb, forefinger and middle finger of right hand are stretched mutually perpendicular to each other such that the forefinger points the direction of magnetic field, thumb points towards the direction of magnetic force, then middle finger points towards the direction of induced current in the conductor.

Notes Of Electromagnetic Induction Class 12
9. The induced emf developed between two ends of conductor of length l rotating about one end with angular velocity ω in a direction perpendicular to magnetic field is given by,

Physics Chapter 6 Class 12 Notes
10. The induced emf can be produced in a coil by
(i) putting the coil/loop/circuit in varying magnetic field.
(ii) changing the area A of the coil inside the magnetic field,
(iii) changing the angle 0 between B and A.

CBSE Notes

Here are the detailed Magnetism And Matter Class 12 Notes Chapter 5. Thus the notes will be very helpful in preparation for examinations. Class 12 Physics notes cover all the important topics that are listed. It gives students a basic understanding of the past and the development of laws in physics. https://meritbatch.com/magnetism-matter-cbse-notes-class-12-physics/

Magnetism And Matter Class 12 Notes Chapter 5

Magnetism And Matter Class 12 Notes
1. The magnetic dipole moment of a magnetic dipole is given by
M = m × 2I
where, m is pole strength and 2I is dipole length directed from S to N.

The SI unit of magnetic dipole moment is A-m² or J/T.
It is a vector quantity and its direction is from South pole to North pole.
Magnetism And Matter Notes
2. Coulomb’s Law in Magnetism
Magnitude of force acting between two magnetic poles is given by

where, m₁ and m₂ are magnetic strength of poles and k is magnetic force constant. Its SI unit is A-m.
Magnetism And Matter
3. Magnetic Field Lines These are imaginary lines which give pictorial representation for the magnetic field inside and around the magnet.
Their properties are given as below:
(i) These lines form continuous closed loops.
(ii) The tangent to the field line gives direction of the field at that point.
(iii) Larger the density of the lines, stronger will be the magnetic field.
(iv) These lines do not intersect one another.


NOTE: The direction of magnetic field between the poles of the dipole is in the direction opposite to the magnetic moment (South to North) while inside the current loop it is in the same direction to that of magnetic moment.
5. Torque on a bar magnet in a uniform magnetic field is

where, θ is the angle between M and B. Its SI unit is joule per tesla (JT^-1).
Class 12 Magnetism And Matter Notes
6. Potential energy of a magnetic dipole in a magnetic field is given by
U = – MB cos θ = – M . B where, θ is the angle between M and B.
7. Work done in rotating the dipole in a uniform magnetic field from θ₁ to θ₂ is given by
W = MB (cos θ₁ – cos θ₂)
Physics Chapter 5 Class 12 Notes
8. Current loop behaves like a magnetic dipole whose dipole moment is given by
M=IA
The direction of dipole moment can be obtained by right hand thumb rule. Its. SI unit is A-m².
9. Magnetic dipole moment of a revolving electron is given by

where, v is speed of electron on a circular path of radius r.
L is angular momentum and given as L – mvr.
10. Interaction between two magnetic dipoles is

Notes Of Magnetism And Matter
11. Oscillation of a Freely Suspended Magnet The oscillations of a freely suspended magnet (magnetic dipole) in a uniform magnetic field are SHM.

where, I = moment of inertia of the magnet, M = magnetic moment and B = magnetic field intensity.
12. Bar Magnet as an Equivalent Solenoid The expression of magnetic field at distance r from centre is given by

This expression is equivalent to that of bar magnet.
13. The Electrostatic Analog
The table given below summarises the analogy between electric and magnetic dipoles

Class 12th Physics Chapter 5 Notes
14. Magnetism and Gauss’ Law
The net magnetic flux (Ф_B) through any closed surface is always zero.

CBSE Notes

These are the How Many Squares? Class 5 Notes Maths Chapter 3 prepared by team of expert teachers. The revision notes help you revise the whole chapter 2 in minutes. Revision notes in exam days is one of the best tips recommended by teachers during exam days. Download CBSE Notes Class 5 Maths for chapter 3 in PDF format for free.  https://meritbatch.com/many-squares-cbse-notes-class-5-maths/

How Many Squares? – CBSE Notes for Class 5 Maths

CBSE NotesCBSE Notes Class 5 MathsNCERT Solutions Maths

Summary:

• Perimeter: The length of the boundary is called Perimeter.
• Area of rectangle = length / breadth
• Area of an irregular shape like footprints, palm, etc. can be obtained by tracing them on a squared sheet paper.

Steps:

(a) Count the number of complete squares.
(b) Count the number of more than half filled squares.
(c) Count the number of less than half filled squares.
(d) Neglect the squares which are less than half filled.
(e) Add the numbers of complete squares and more than half filled squares. This will give the approximate value of area.

Measure the side of the red square on the dotted sheet. Draw here as many rectangles as possible using 12 such squares.

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A Pact with the Sun Summary In English

A Pact With The Sun Summary
Saeeda’s mother had been suffering from fever, cough, body pain and joint pain etc. A number of physicians treated her. The quacks forbade her normal food. They also advised her to remain in the closed room. They asked her to avoid both sunshine and fresh air. Their advice did not help her. In fact she needed sunshine and fresh air for good health.

Then people suggested that she should consult a specialist. She was poor. However, she knew that life was more precious than money. So she consulted a specialist. She sold her ornaments also to meet the expenditure on medicines. The specialist examined her. He prescribed effective but costly medicines. He allowed her to eat anything of her taste. He laid most importance on fresh air and sunlight. He advised her to shift in a big room with doors and windows open. He asked her to sit in the sunlight from eight to nine daily.

A Pact With The Sun Class 6 Summary
Some people opposed the specialist’s advice. Saeeda’s mother did not listen to their proposals. She got her bed moved to a bigger room. She desired to sit in the sun on her cot for an hour daily.

Unluckily, it remained cloudy for a few days. She started lamenting and complaining to God.
Saeeda saw a spot of pale sunshine late in the afternoon. The people forbade Saceda’s mother to bask in the sun. They told her that it was too late and chilly. Saeeda requested the departing rays of the sun to come the next day with enough warmth and brightness. The rays gave her the desired promise because her ailing mother needed their help.

Summary Of A Pact With The Sun
Next day the rays were keen to go to the earth early in the morning. After all they had given a word to Saeeda. But the sun said. “It’s our day off again. The road to earth is blocked by the clouds”. The ray who had given its word to Saceda said, “Sir, I can’t stay back …… I’ll pierce the clouds to reach Saeeda’s courtyard.”

The sunrays revolted against the sun to keep their honour. They focused their heat and the clouds scattered. The sunrays reached the earth a bit late. Saeeda’s mother basked in the sun and breathed in fresh air. Her pale face glowed. The doctor’s advice had a magical effect on her. She is fully recovered now.

A Pact with the Sun Summary In Hindi

साईदा की अम्माँ, ज्वर, खांसी, शरीर-दर्द तथा जोड़ों के दर्द आदि से पीड़ित थी। अनेकों चिकित्सकों ने उसका उपचार किया। नीम-हकीमों ने उसका सामान्य भोजन भी बन्द कर दिया। उन्होंने उसे बन्द कमरे में रहने की सलाह भी दी। उन्होंने उसे धूप और ताजी हवा से बचने के लिए कहा। उनकी सलाह से उसे कोई लाभ नहीं हुआ। वास्तव में अच्छे स्वास्थ्य के लिए उसे धूप और ताजी हवा की आवश्यकता थी।

A Pact With The Sun Class 6 Chapter 1 Summary In Hindi
तब लोगों ने कहा कि वह किसी विशेषज्ञ की सलाह ले। वह गरीब थी। फिर भी वह जानती थी कि जीवन धन से अधिक कीमती है। अतः उसने किसी विशेषज्ञ से परामर्श किया। उसने अपने आभूषण भी बेच दिए ताकि दवाइयों पर किया गया खर्च वहन कर सके। विशेषज्ञ ने उसका निरीक्षण किया। उसने प्रभावकारी परन्तु महँगी दवाइयाँ निर्दिष्ट कीं। उसने उसे छूट दी कि वह अपनी रुचि के अनुसार कोई भी भोजन ले सकती थी। उसने सबसे अधिक महत्त्व ताजी हवा और धूप को दिया। उसने उसे सलाह दी कि वह अपनी जगह बदल कर किसी खुले दरवाजे और खिड़कियों वाले बड़े कमरे में जाये। उसने उसे सलाह दी कि वह धूप में आठ से नौ बजे तक प्रतिदिन बैठे।

कुछ लोगों ने विशेषज्ञ की नसीहत का विरोध किया। साईदा की अम्माँ ने उनके प्रस्तावों की ओर ध्यान नहीं दिया। उसने अपने पलंग को अधिक बड़े कमरे में डलवा लिया। वह प्रतिदिन एक घंटा अपनी चारपाई के ऊपर धूप में बैठना चाहती थी।

Class 6 English Chapter 8 A Pact With The Sun Summary
दुर्भाग्य से, कुछ दिनों तक बादल छाए रहे। वह विलाप करने और भगवान से शिकायत करने लगी।
मध्याह्न के बाद, साईदा को पीली धूप वाला कुछ स्थान नजर आया। लोगों ने साईदा की अम्माँ को धूप सेकने से मना कर दिया। उन्होंने कहा कि यह बड़ी देर का और अत्यधिक कँपकँपी लाने वाला समय है। साईदा ने सूर्य की बिछुड़ती हुई ‘किरणों से प्रार्थना की कि वे कल काफी गर्मी और रोशनी लेकर अवश्य आएँ। किरणों ने उसे मनचाहा वचन दिया क्योंकि उसकी बीमार अम्माँ को उनकी सहायता की आवश्यकता थी।

अगले दिन बड़े सवेरे किरणें पृथ्वी पर जाने के लिए उत्सुक थीं। आखिर उन्होंने साईदा को वचन दे रखा था। परंतु सूर्य ने कहा ” आज फिर हमारी छुट्टी है। धरती पर जाने का मार्ग बादलों ने रोक रखा है।” जिस किरण ने साईदा से वायदा कर रखा था वह बोली, ” श्रीमन्, मैं रुक नहीं सकती …… साईदा के आंगन में पहुँचने के लिए मैं बादलों को चीर दूंगी।”

A Pact With The Sun Class 6 Chapter 1 Summary
किरणों ने अपने सम्मान को कायम रखने के लिए सूर्य के विरुद्ध विद्रोह कर दिया। उन्होंने अपनी गर्मी को केन्द्रित किया और बादल छट (तितर-बितर हो) गए। सूर्य की किरणें थोड़ी देर से पृथ्वी पर पहुँचीं। साईदा की अम्माँ ने धूप का आस्वादन किया और स्वच्छ वायु में सांस लिया। उसका पीला चेहरा चमक उठा। डॉक्टर की नसीहत का उसके ऊपर चमत्कारी प्रभाव पड़ा। अब वह पूरी तरह से ठीक हो गई है।

The CBSE Class 6 English Notes and Summary will also help students in their English exam preparation. The Wonder Called Sleep Summary Class 6 English has been formatted in a simple language enabling you to read it and get hold of what the author wants us to understand. https://meritbatch.com/the-wonder-called-sleep-summary/

The Wonder Called Sleep Summary In English

The Wonder Called Sleep Summary
Sleep is a state of unconscious rest. Our day’s activities cause tiredness. A good sleep provides rest to our body and mind. When we sleep, our body recovers from exertion. This is the most obvious advantage of sleep.

Many things happen to us during sleep. We forget most of those happenings when we wake up. Sometimes we remember a dream. Our muscles relax more and more when we enjoy a sound sleep. Our heart beat becomes slower. Our blood pressure and temperature go down then. The brain also slows down. We cannot think or act consciously. These things become normal when we wake up.

The Wonder Called Sleep Summary In Hindi
Sometimes we dream during sleep. We forget most of our dreams by the time we wake up.
Dream is an important activity of the mind. It enables us to sleep even through noisy disturbances. Our dreams mostly reveal our problems. They can also provide a solution of the related problems.

But we must remember one thing. Dreams can never tell the future.
Sleep has wonderful powers. It transports us into a strange land. We forget even our near and dear ones then. Sleep is the sweetest and most common experience. So it is rightly called a wonder.

The Wonder Called Sleep Summary In Hindi

निद्रा, चेतनारहित विश्राम की स्थिति होती है। दिन भर हमारे द्वारा किए जाने वाले कार्य थकावट पैदा करते हैं। गहरी नींद, हमारे शरीर और मस्तिष्क को आराम देती है। जब हम नींद लेते हैं, तब हमारा शरीर थकावट से मुक्त हो जाता है। निद्रा का यह सबसे स्पष्ट लाभ है।

Summary Of The Wonder Called Sleep
नींद के दौरान, बहुत सारी बातें हमारे साथ घटित होती रहती हैं। जब हम जाग जाते हैं तब बहुत-सी बातों | को भूल जाते हैं। कई बार हमें कोई स्वप्न याद रह जाता है। जिस समय हम गहरी नींद का आस्वादन करते हैं, उस समय हमारी मांसपेशियाँ अधिक से अधिक विश्राम करती हैं। हमारे हृदय की गति मन्दतर हो जाती है। उस समय |हमारा रक्तदाब और तापमान भी कम हो जाता है। मस्तिष्क की गति भी धीमी हो जाती हैं। हम चेतन मन से कुछ सोच या कर नहीं सकते। ये सारी बातें हमारे जागने पर सामान्य हो जाती हैं।

कई बार, हम नींद के दौरान स्वप्न देखते हैं। जागने से पहले हम अपने अधिकतर स्वप्नों को भूल जाते हैं।
स्वप्न, मस्तिष्क की एक महत्त्वपूर्ण क्रिया है। यह हमें शोरयुक्त विघ्नों के बीच भी नींद लेने की शक्ति प्रदान करती है। हमारे स्वप्न, बहुधा, हमारी समस्याओं को उजागर करते हैं। वे सम्बन्धित समस्याओं का हल भी प्रदान कर सकते हैं।

The Wonder Called Sleep Meaning In Hindi
परंतु हमें एक बात अवश्य याद रखनी चाहिए। स्वप्न कभी भविष्य नहीं बता सकते हैं।
निद्रा में विस्मयकारी शक्तियां निहित होती हैं। यह हमें अनजान स्थानों पर ले जाती है। तब हम अपने नजदीकी तथा प्रियतम व्यक्तियों को भी भूल जाते हैं। नींद, मधुरतम तथा सर्वाधिक सामान्य अनुभव है। अतः इसे ठीक ही एक विस्मय कहा गया है।