Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?

Explain how Corpuscular theory predicts the speed of light in a medium, say, water, to be greater than the speed of light in vacuum. Is the prediction confirmed by experimental determination of the speed of light in water? If not, which alternative picture of light is consistent with the experiment?

Let us list some of the factors, which could possibly influence the speed of wave propagation:

(i) Nature of the source

(ii) Direction of propagation

(iii) Motion of the source and/or observer

(iv) Wavelength

(v) Intensity of the wave

On which of these factors, if any, does the speed of light in vacuum?

In an intrinsic semiconductor the energy gap E_gis 1.2 eV. Its hole mobility is much smaller than electron mobility and independent of temperature. What is the ratio between conductivity at 600K and that at 300K? Assume that the temperature dependence of intrinsic carrier concentration n_iis given by

`"n"_"i" = "n"_0 exp(- "E"_"g"/(2"k"_"BT"))`

where n₀ is a constant.

Find the condition under which the charged particles moving with different speeds in the presence of electric and magnetic field vectors can be used to select charged particles of a particular speed.

Asha's mother read an article in the newspaper about a disaster that took place at Chernobyl. She could not understand much from the articles and asked a few questions from Asha regarding the article. Asha tried to answer her mother's questions based on what she learnt in Class XII Physics.

(a) What was the installation at Chernobyl where the disaster took place? What according to you, was the cause of this disaster?

(b) Explain the process of release of energy in the installation at Chernobyl.

(c) What according to you, were the values displayed by Asha and her mother?

Explain the term demodulation used in a communication system.

A photosensitive surface emits photoelectrons when red light falls on it. Will the surface emit photoelectrons when blue light is incident on it? Give reason. 

Distinguish between broadcast mode and point-to-point mode of communication and give one example for each.

Draw a plot showing the variation of photoelectric current with collector potential for different frequencies but same intensity of incident radiation ?

Use Einstein's photoelectric equation to explain the observations from this graph ?

What change will you observe if intensity of incident radiation is changed but the frequency remains the same?

Depict the behaviour of magnetic field lines in the presence of a diamagnetic material?

A device X used in communication system can convert one form of energy into another. Name the device X. Explain the function of a repeater in a communication system.

Distinguish between point to point and broadcast modes of communication. Give an example of each.

Explain the basic concept of mobile telephoning ?

Two identical coils P and Q each of radius R are lying in perpendicular planes such that they have a common centre. Find the magnitude and direction of the magnetic field at the common centre of the two coils, if they carry currents equal to I and \[\sqrt{3}\] I respectively.

Distinguish between point to point and broadcast modes of communication. Give an example of each.

A point charge q moving with speed v enters a uniform magnetic field B that is acting into the plane of the paper as shown. What is the path followed by the charge q and in which plane does it move?

 If an electric field \[\vec{E}\] is also applied such that the particle continues moving along the original straight line path, what should be the magnitude and direction of the electric field \[\vec{E}\] ?