Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Physics

The mutual inductance M₁₂ of coil 1 with respect to coil 2 ______.

1. increases when they are brought nearer.
2. depends on the current passing through the coils.
3. increases when one of them is rotated about an axis.
4. is the same as M₂₁ of coil 2 with respect to coil 1.

There are two coils A and B seperated by some distance. If a current of 2A flows through A, a magnetic flux of 10^-2 Wb passes through B (no current through B). If no current passes through A and a current of 1A passes through B, what is the flux through A?

In a Young’s double slit experiment, the source is white light. One of the holes is covered by a red filter and another by a blue filter. In this case ______.

Why is the diffraction of sound waves more evident in daily experience than that of light wave?

Consider a two-slit interference arrangement (Figure) such that the distance of the screen from the slits is half the distance between the slits. Obtain the value of D in terms of λ such that the first minima on the screen falls at a distance D from the centre O.

The wavelength of a photon needed to remove a proton from a nucleus which is bound to the nucleus with 1 MeV energy is nearly ______.

1. In the explanation of photo electric effect, we assume one photon of frequency ν collides with an electron and transfers its energy. This leads to the equation for the maximum energy E_max of the emitted electron as E_max = hν – φ₀  where φ₀ is the work function of the metal. If an electron absorbs 2 photons (each of frequency ν) what will be the maximum energy for the emitted electron?
2. Why is this fact (two photon absorption) not taken into consideration in our discussion of the stopping potential?

There are materials which absorb photons of shorter wavelength and emit photons of longer wavelength. Can there be stable substances which absorb photons of larger wavelength and emit light of shorter wavelength.

A student performs an experiment on photoelectric effect, using two materials A and B. A plot of V_stop vs ν is given in Figure.

1. Which material A or B has a higher work function?
2. Given the electric charge of an electron = 1.6 × 10^–19 C, find the value of h obtained from the experiment for both A and B.

Comment on whether it is consistent with Einstein’s theory:

The simple Bohr model is not applicable to He 4 atom because ______.

1. He⁴ is an inert gas.
2. He⁴ has neutrons in the nucleus.
3. He⁴ has one more electron.
4. electrons are not subject to central forces.

Imagine removing one electron from He⁴ and He³. Their energy levels, as worked out on the basis of Bohr model will be very close. Explain why.

In Figure, Vo is the potential barrier across a p-n junction, when no battery is connected across the junction ______.

In the circuit shown in figure, if the diode forward voltage drop is 0.3 V, the voltage difference between A and B is ______.

When an electric field is applied across a semiconductor ______.

1. electrons move from lower energy level to higher energy level in the conduction band.
2. electrons move from higher energy level to lower energy level in the conduction band.
3. holes in the valence band move from higher energy level to lower energy level.
4. holes in the valence band move from lower energy level to higher energy level.

Consider an npn transistor with its base-emitter junction forward biased and collector base junction reverse biased. Which of the following statements are true?

1. Electrons crossover from emitter to collector.
2. Holes move from base to collector.
3. Electrons move from emitter to base.
4. Electrons from emitter move out of base without going to the collector.

Consider an npn transistor with its base-emitter junction forward biased and collector base junction reverse biased. Which of the following statements are true?

1. Electrons crossover from emitter to collector.
2. Holes move from base to collector.
3. Electrons move from emitter to base.
4. Electrons from emitter move out of base without going to the collector.

Figure shows the transfer characteristics of a base biased CE transistor. Which of the following statements are true?

At V_i = 0.4 V, transistor is in active state.

At V_i = 1 V, it can be used as an amplifier.

At V_i = 0.5 V, it can be used as a switch turned off.

At V_i = 2.5 V, it can be used as a switch turned on.

In the depletion region of a diode ______.

1. there are no mobile charges.
2. equal number of holes and electrons exist, making the region neutral.
3. recombination of holes and electrons has taken place.
4. immobile charged ions exist.

The breakdown in a reverse biased p–n junction diode is more likely to occur due to ______.

1. large velocity of the minority charge carriers if the doping concentration is small.
2. large velocity of the minority charge carriers if the doping concentration is large.
3. strong electric field in a depletion region if the doping concentration is small.
4. strong electric field in the depletion region if the doping concentration is large.

Can the potential barrier across a p-n junction be measured by simply connecting a voltmeter across the junction?