TyroCity: Physics XII Notes

Nature and Propagation of Light

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short

Differentiate between a plane wave front and a spherical wave front.
Which parameter of light does not change on refraction?
Define accommodation of eye and its near point.
What is Huygens principle?
When monochromatic light incidents on a surface, the reflected and refracted wave will have same frequency. Why?
State Huygens principle. Does it apply to sound waves in air?
What is a wave front?

Long

State and explain Huygens principle. Use the principle to show that a plane wave front incident obliquely on a plane mirror is reflected as a plane wave front so that angle of incidence is equal to the angle of reflection.
Prove the law of reflection of light using the wave theory?
Define Huygen’s principle and prove Snell’s law by the help of wave theory of light. State and explain Huygen’s principle. Use the principle to show that a plane wave front incident obliquely on a plane reflecting surface is reflected as a plane wave front so that the angle of incidence is equal to the angle of reflection.
Describe Michelson’s method for the determination of speed of light. Write advantages of the method over Foucault’s method.
State and explain Huygen’s principle. Use the principle to show that a p lane wave incident obliquely on a plane mirror is reflected as a plane wave so that the angle of incidence is equal to the angle of reflection.
Describe Foucault’s method for the determination of speed of light.

DC Circuit

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Questions

An ammeter is always connected in series. Why?
Why do we use connecting wires made of copper?
What are the factors on which the resistance of a conductor depends?
Can the potential difference across a battery be greater than its emf?
Two bulbs of 60 W and 100 W are connected in series and this combination is connected across the mains. Which bulb will glow more brightly? Give reason.
You are given n wires each of resistance rΩ. What is the ratio of maximum to minimum resistance that can be obtained from these wires?
Is terminal p.d. always connected in parallel with the load resistance?
Two bulbs have the filament of the same length. If one is of 40 watt and the other 60 watt, which one has thicker filament?
Two bulbs have the filament of the same length. If one is of 40 watt and the other 60 watt, which one has thicker filament?
Why are alloys constantan and manganin used to make standard resistors?
A large number of free electrons are present in metals. Why is there no current in the absence of electric field across it?
Explain the significance of a shut with a diagram.
The element of heater is very hot while the wire carrying current are cold, why?
You are given 2 wires each of resistance R. What is the ratio of maximum to minimum resistance that can be obtained from these wires?
Why heat is generated across a resistor when the electric field is applied?
Why do electric acquire a steady drift velocity?
Why ammeter is always connected in series?
A wire is stretched to double its length. What happens to its resistance?
The energy that can be extracted from a storage battery is always less than the energy that goes into it while charging. Why?
The resistance of an ammeter must essentially be very small. Why?
Water boils in an electric kettle in 15 after being switched on. Using the same main supply. Should the length of the heating element be increased or decreased if the water is to boil in 10 minutes? Explain.
What is the ratio of maximum to minimum resistance obtained from n wires of resistance R each?
Why is it essential that the resistance of a voltmeter be very high?
An ammeter is always connected in series. Why?
Distinguish between resistance and resistivity of a material.
Long-distance, electric power, transmission lines always operate at very high voltage, some time as much as 750 kV. What are the advantages of such high voltage?
Distinguish between resistance and resistivity. Derive expressions for the effective resistance of number of resistors connected in series and parallel.

Long Questions

Deduce an expression for the heat developed in a wire by the passage of an electric current.
What do you mean by a shunt? Describe its use in converting a galvanometer into an ammeter.
What is drift velocity of an electron? Derive a relation between the current through a metallic conductor and the drift velocity in terms of the number of free electrons per unit volume of the conductor.
Discuss the mechanism of metallic conduction. Derive j=new where j is the current density, e is the electronic charge and v is drift velocity.
State and explain joule`s laws of electric current. Discuss how they are verified experimentally.
What do you meant by shunt? How will you convert a galvanometer into an ammeter?
State and explain Ohm`s law. Two resistors are connected in parallel and third resistor be connected in series with the combination of parallel resistors. If this combination be connected with a battery of the negligible internal resistance, find the potential difference across each resistor.
What is meant by a shunt? How will you convert a galvanometer into a ammeter?
Discuss the mechanism of metallic conduction. Derive a relation between current density and drift velocity.

Acoustic Phenomena

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Answer Questions

How are beats produced? What is beat frequency?
What are ultrasonic and infrasonic?
Distinguish between ultrasonic and supersonic’s.
How it is that one can recognize a friend from his voice without seeing him?
Why is it roaring of a lion different than the sound of a mosquito?
What do you mean by the term threshold of hearing?
Whistle of an approaching train is shriller. Why?
Define beats and beat frequency.
Bells are made of metal and not of wood, why?
Explain with a figure the meaning of beats.
Two notes, one produced by violin and the other by a sitar, may have the frequency, yet we can distinguish between them. Why?
Which has a more direct influence on the sound wave: the observer is approaching the stationary sound source.
What is meant by threshold of hearing?

Long

Deduce the expressions for the frequency herd by an observer, when the observer is approaching the stationary sound source.
What is Doppler`s effect? Derive an expression for the apparent frequency received by a stationary observer when a source is moving away from him.
What do you mean by intensity and intensity level of sound? Define bel and decibel.
What are beats? Prove that the number of beats per second is equal to the difference between the frequencies of two superposing waves.
What is Doppler`s effect? Derive the change in frequency when an observer moves towards a stationary source?
Discuss the phenomenon of Doppler`s effect. Find the change in frequency when a moving source of sound passes a stationery observer.
Define intensity of sound. Show that the intensity of sound for a given frequency is directly proportional to the square of amplitude of vibration.

8 Define the intensity of sound and prove that l=1/2pVr2w2 where the symbols have their usual meaning.

What is the Doppler Effect in sound? Obtain an expression for the apparent frequency of the sound when the source and observer both move in the same direction.
Define intensity and deduce it in terms of amplitude of vibration, density of medium, angular velocity and velocity of the wave.
What are beats? Obtain an expression for the beat frequency when beats are produced by superposing two waves of slightly different frequencies.
What is Doppler`s Effect? Deduce an expression for the apparent frequency heard by a stationary observer when a source approaches towards him.

Mechanical Waves: Important Questions

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

What do you mean by water waves?
Why sound produced at a distance can be heard distinctly at night than in day time?
Is velocity of sound more in damp air or in dry air? Explain.
A boat at anchor is rocked by waves whose crest is 100 feet apart and whose velocity is 25 feet /s. These reach the boats once in every t s. What is the value of t?
Ultrasonic, infrasonic and audio waves travel through a medium with velocity vu, vi, varespectively. Then what is the relationship among them?
A man stands on the ground at a fixed distance from a siren whit emits a sound of fixed amplitude.
The ratio of velocity of sound in hydrogen gas r=7/5 to that on helium gas r= 5/3 at the same temperature is VH:VHe, what is the value of this ratio?
The velocity of sound in a tube containing air at 27°C at the pressure of 760 cm of Hg is 330 m/s. What will be the velocity of sound when the pressure is increased to 100 cm of Hg and temperature is kept constant?
A uniform rod of length L and mass M hangs freely from a fined point. Then the velocity of transverse wave along the rod at a distance x from the free end is v m/s. What is its value?
In a ripple tank when one pulse is sent every 10th of a second, the distance between consecutive pulses is 30 mm. in the same depth of water pulse are produced in half second intervals. What is the distance between consecutive pulses?
If you are walking on the moon surface, can you hear the cracking sound behind you? Explain.
Do sound waves need a medium to travel from one point to other point in space? What properties of the medium are relevant?
Why velocity of sound in solid is more than that in liquid?
Why velocity of sound in liquid is more than that in air?
Why velocity of sound in hydrogen is more than that in air?
What are the draw backs of Newton’s formula for the velocity of sound in air? What is the Laplace’s correction?
What is the sound of clock tower heard feebly at large distance than near to it?
What is beat? How a musician can use this effect to tune string instrument?
What is threshold of hearing and threshold of pain?
Why are beats produced? What is beat frequency?
What is it that one can recognize a friend from his voice without seeing him?
Whistle of an approaching train is shriller. Why?
Although the density of solid is high, the velocity of sound is greater in solid, explain.
Why is roaring of the lion different than that of mosquito?
What is persistence of hearing? Also define threshold of hearing (or audibility) threshold.
Why is the wall at the back of the stage in a big hall made parabolic?
A stone is dropped from the top of the tower 300m high splashes into the water of a pond near the base, of the tower. When is the splash heard at the top? Given that the speed of sound in air is 340 m/s, g= 9.8 m/s [ ans= 8.70 s]
The audible frequency range of a human air is 20Hz to 20KHz. Convert this into the corresponding wavelength range. V of sound on air = 340 m/s.
Draw the graph for beat phenomenon.

Diffraction

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Diffraction grating is better than a two –slit set up for measuring the wave length of monochromic light. Explain.
What is diffraction of light?
Radio waves diffract around building but light waves do not. Why?
The diffraction of sound waves is more evident in daily experience than that of light waves, why?
Describe what happens to the single slit diffraction pattern when the width of the slit is less than the wave length of the wave.
What is self-inductance? Define coefficient of self-inductance.
What is diffraction of light? How does it differ from interference of light?
Describe the diffraction of light at a single slit and find the condition for secondary maxima and minima.
What are the difference between interference and diffraction? Explain the theory of diffraction off light through a single slit.
Describe diffraction of light through a single slit.
What is the basic difference between interference and diffraction? Discuss Fraunhofer diffraction at a single slit.
What is Fraunhoffer diffraction? Explain the formation of maxima and minima due to diffraction? Show that the width of central maxima is inversely proportional to the distance between the two slits.

Polarization

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short answers question

Can sounds waves be polarized? Explain.
Is polarization possible for longitudinal waves? Why?
Light waves can be polarized. What about sound waves? Explain.
What is polarizing angle? Does it depend on the wavelength of light?
The polarizing angle for a transparent medium is 600. What is the refractive index of the medium?

Long answers question

Distinguish between a plane polarized and unpolarized light.
Show that: tan p=n
Where
n=refractive index of the medium
p=angle op polarization of polarizing angle.
What do you mean by polarization of electromagnetic waves? Discuss the polarization of light by refection and show that , where the symbols have their usual meanings.
What is polarizing angle? Derive the relation between the polarizing angle and the refractive index of the medium.

Mechanical Waves

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short

Why sound made/produced at a distance can be heard distinctly at night than in the day time?
Is velocity of sound more in damp air or in dry day?

3.Why sounds are heard better on a wet day than on a dry day?

Do sound waves need a medium to travel from one point to other point in space? What properties of the medium are relevant?
Although the density of solid is high, the velocity of sound is great in solid, explain.
Explain why the velocity of sound in solids is greater than that in gases, though the densities of solids are greater than that of gases.
Sound at distances can be heard distinctly at night than in the day time. Why?
Velocity of sound increases on a cloudy day. Why?
Sound travels faster in metal than in air, why?
Can two persons on hear the sound of each other? Explain.

Long

Discuss the effect of pressure, temperature and density of elastic medium on the velocity of sound.
What is Newton`s formula for the velocity of sound? What correction was made by Laplace?
Describe Newton`s expression for the velocity of sound in a gas.
Derive an expression for the velocity of sound in a medium by dimensional method. Discuss the effect of change in pressure and temperature on the velocity of sound in air.
Discuss Laplace`s correction and derive the formula for the velocity of sound in a gas.
State Newton`s formula for the velocity sound in gases. What correction was done by Laplace on it?
Explain the significance of Laplaces correction of Newtons formula for the velocity of sound derive the corrected formula.
Write down the factors on which the velocity of sound in air depends with necessary explanation.
Discuss Newtons formula for the velocity of sound in a gas with Laplaces correction.
Discuss Newtons formula for the velocity of sound in air with Laplaces correction.
Write an expression for the speed of sound in an ideal gas. Discuss the effect of change in temperature on the speed of sound.

Magnetic effect of current

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Questions

Under what conditions do a charge affect a magnet?
State Ampere’s theorem
Does a charged particle moving through a magnetic field experience a force? Express with conditions, maximum, and minimum force it experiences.
A portion moving in a straight line enters a strong magnetic field along the field direction. How will its path and velocity change?
Why is the cylindrical core of soft iron used in moving coil galvanometer?
Define an Ampere in terms of the force between current carrying conductors.
How magnetic field is made radial in a moving coil galvanometer?
Explain how the direction of Lorentz force is determined.
A current carrying solenoid tends to contract, why?
A solenoid tends to contract when a current passes through it, why?
What will be the effect if the magnetic field in a moving coil galvanometer is not radial?
An electron beam and a portion beam are moving parallel to each other is the beginning. Do they always maintain this status? Justify your answer.
Deduce an expression for the force between two parallel current carrying conductors. Define one ampere current.
State Ampere`s circuital theorem.

Long Questions

State Biot-Savart law and obtain the expression for the magnetic field at the centre of the circular coil.
Explain in brief, the motion of an electron moving normal to a magnetic field.
Derive an expression for the magnitude of the magnetic flux density at the centre of a narrow circular coil.
Derive an expression for the magnetic field at a point due to a long straight conductor carrying current.
What is a Helmholtz coil? Derive an expression for the magnetic field due to this coil.
Derive the formula for the magnetic field at the centre of the circle of a circular coil carrying current. Explain why the magnetic field at the centre of the coil disappears when the circular coil is made infinitely large.
State and explain Ampere`s theorem and hence use it to find the magnetic field intensity due to a long current carrying solenoid.
Derive the formula for the magnetic field at a point due to a long straight current carrying conductor using Biot- Savart law.
State and explain Biot-Savart law and hence use it to find the magnetic field intensity at any point due to a long straight conductor.
Find an ex expression for torque on rectangular coil in a uniform magnetic field.
What is a Helmholtz coil? Derive an expression for the magnetic field due to this coil.
State and explain Biot-Savart law. Use this law to find the magnetic field intensity at any point due to a long straight current carrying conductor.
State and explain Boit-Savart law with a case of its application.
Derive an expression of force per unit length between two parallel conductors separated by distance ‘r’ and carrying currents l1 and l2 in the same direction.
State and explain Biot-Savart law. Use it to find the magnetic field at the center of a circular coil of N turns and carrying current l.
Find an expression for the magnetic field on the axis of a solenoid, carrying current, using Ampere`s law.
Obtain magnetic field straight at a point on the axis of circular current loop by using Biot and Savart law.
State and explain Ampere`s theorem and hence use it to find the magnetic field due to a long solenoid carrying current l.
Straight and explain Biot-Savart law and hence use this law to find the magnetic field to a long straight current carrying conductor.
What is a Helmholtz coil? Derive an expression for the uniform magnetic field obtained from it.

Free question test - Physics 12

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Current Electricity

Discuss the mechanism of metallic conduction. Derive a relation between current density and drift velocity.
How is a galvanometer converted into an ammeter and to voltmeter? Explain?
Distinguish between resistance and resistivity. Derive expression for the effective resistance of number of resistors, connected in series and parallel.
Wave and Sound
What is resonance? How is the velocity of sound in air determined by resonance tube method?
What is the principle of super position as applied to wave motion? Discuss, the result of superposing two waves of equal amplitude and same frequency travelling in opposite direction.
What do you mean by phase oscillation and phase constant? Establish the equation of progressive wave.
Magnetic Effect if Current
Define radial magnetic field. Derive an expression for the torque on a rectangular coil in a uniform magnetic field and mention the condition for maximum and minimum torque.
Derive an expression for the magnetic field intensity at a point due to a current carrying straight conductor of infinity length, using Biot-Savart law.
Obtain an expression for the torque acting on a rectangular coil in a uniform magnetic field and also define magnetic moment.

Modern Physics

Describe J.J. Thomson’s experiment for determining the specific charge of an electron.
Describe the phenomenon of electrical discharge through gases.
Describe with necessary theory of Millikan’s oil drop experiment to determine the value of the charge particle in electric and magnetic field.
Discuss the productivity of cathode ray and its characteristics.

Interference

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Answer Questions

Can two independent sources of light produce interference?
Why have the two sources of light to be close to each other for the production of good interference pattern?
Distinguish between interference and diffraction. What do you understand by coherent sources?
In young’s double slit experiment, how is the fringe width altered if the separation between the slits is doubled and the distance between the slits and the screen is halved?
What are the conditions for sustained interference of light?
In Young’s double slit experiment, how is the fringe width altered if the separation between the slits is doubled and the distance between the slits and the screen is halved?
What do you understand by the coherent sources of light?

Long Answer Questions

Derive the fringe width from Young’s double slit experiment.
What do you understand by interference of light? Derive an expression for the fringe width in a Young’s double slits experiment.
Describe Young’s double slits experiment for the interference of light and show that widths of bright and dark fringes are the same.
Prove analytically that the bright and dark fringes in young’s double slit experiment are equally spaced.
Draw a clear ray diagram to illustrate the action of a compound microscope. Also derive an expression for its magnifying power.
Describe Young’s double slit experiment, if brief, for the measurement of wave=length of a monochromatic source of light.
Where is the near point of an eye for which a spectacle lens of power +2D is prescribed?

Electromagnetic Induction

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Questions

What is Lenz’s law?
Mention two types of loss in a transformer.
Show that Lenz’s law is an example of conservation of energy.
Two closely would circular coils have the same number of turns, but one has twice the radius of the other. What is the ratio of self inductance’s of the two coils?
Why can`t a transformer be used to change the value of d.c. voltage?
What is eddy current? Write down its uses?
What are different power losses in a transformer? What measures do you take to minimize these losses?
Why can`t a transformer be used to step up or down the d.c. voltage?
A transformer cannot be used in do circuits, why?
State Faraday`s laws of electromagnetic induction.
A sheet of copper is placed between the poles of an electromagnet with the magnetic field perpendicular to the sheet. When it is pulled out, a considerable force is required, and the force required increases with speed, why?
Permanent magnets are made of steel while the core of transformer is made of soft iron. Why?
A student asserted that if a permanent magnet is dropped down a vertical copper pipe, it eventually reaches a terminal velocity even if there is no air resistance. Why should this be?
If a permanent magnet is dropped down a vertical copper pipe, it eventually reaches a terminal velocity even if there is no air resistance. Why should this be?
Describe the theory and working of an a.c. generator.

Long Questions

Obtain the expression for the emf induced in the conductor moving in a magnetic field.
State the laws of electromagnetic induction. Derive an expression for the emf induced in a conductor moving in a magnetic field.
Deduce an expression for induced emf in a coil rotating in a magnetic field.
State Lenz`s law and explain how this law leads to the conservation of energy principle.
State Faraday`s laws of electromagnetic induction. Deduce an expression for induced emf in a coil rotating in a magnetic field.
State and explain Faraday`s law of electromagnetic induction. Derive an expression for the induction a coil rotating in a uniform magnetic field.
State Faraday`s law of electromagnetic induction. Derive an expression for the induced in a straight conductor moving at right angle to the direction of a uniform magnetic field.
A metallic rod is moving in a magnetic field. Determine the emf induced across it.

Wave Motion

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Wave motion

Short Questions

How are stationary waves formed?
If you are moving on the moon surface, can you hear the cracking sound behind you? Explain.
Do sound waves undergo reflection, refraction and polarization phenomena? Explain.
Which type of wave propagates in liquid, explain.
Longitudinal waves cannot be polarized. Why?
Distinguish between light waves and sound waves.

Long Questions

Use the principle of superposition of two waves to find the position of displacement of nodes and antinodes in standing waves?
State and explain the stationary waves?
Define progressive wave. Derive progressive wave equation.
What do you mean by progressive wave equation? Derive progressive wave equation in terms of its wave vector and displacement.
What the principle of superposition is as applied to wave motion? Discuss, the result of superposing two waves of equal amplitude and same frequency travelling in opposite direction.