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

Consider sunlight incident on a slit of width 10⁴ A. The image seen through the slit shall ______.

Consider sunlight incident on a pinhole of width 10³A. The image of the pinhole seen on a screen shall be ______.

1. a sharp white ring.
2. different from a geometrical image.
3. a diffused central spot, white in colour.
4. diffused coloured region around a sharp central white spot.

Photons absorbed in matter are converted to heat. A source emitting n photon/sec of frequency ν is used to convert 1 kg of ice at 0°C to water at 0°C. Then, the time T taken for the conversion ______.

1. decreases with increasing n, with ν fixed.
2. decreases with n fixed, ν increasing.
3. remains constant with n and ν changing such that n ν = constant.
4. increases when the product n ν increases.

There are two sources of light, each emitting with a power of 100 W. One emits X-rays of wavelength 1 nm and the other visible light at 500 nm. Find the ratio of number of photons of X-rays to the photons of visible light of the given wavelength?

Which one of the following cannot emit radiation and why? Excited nucleus, excited electron.

In pair annihilation, an electron and a positron destroy each other to produce gamma radiation. How is the momentum conserved?

A 220 V A.C. supply is connected between points A and B (figure). What will be the potential difference V across the capacitor?

The output of the given circuit in figure is given below.

To reduce the ripples in a rectifier circuit with capacitor filter ______.

1. R_L should be increased.
2. input frequency should be decreased.
3. input frequency should be increased.
4. capacitors with high capacitance should be used.

Draw the output waveform across the resistor (Figure).

Assuming the ideal diode, draw the output waveform for the circuit given in figure. Explain the waveform.

The temperature (T) dependence of resistivity of materials A and material B is represented by fig (i) and fig (ii) respectively. Identify material A and material B.

fig. (i)

fig. (ii)

Two concentric and coplanar circular loops P and Q have their radii in the ratio 2:3. Loop Q carries a current 9 A in the anticlockwise direction. For the magnetic field to be zero at the common centre, loop P must carry ______.

With the help of a circuit diagram, explain briefly how a p-n junction diode works as a half-wave rectifier.

Give two differences between a half-wave rectifier and a full-wave rectifier.

A long straight wire of radius 'a' carries a steady current 'I'. The current is uniformly distributed across its area of cross-section. The ratio of the magnitude of magnetic field `vecB_1` at `a/2` and `vecB_2` at distance 2a is ______.

Calculate the self-inductance of a coil using the following data obtained when an AC source of frequency `(200/pi)` Hz and a DC source are applied across the coil.

Read the following paragraph and answer the questions.

1. Explain the reason for the jumping of the ring when the switch is closed in the circuit.
2. What will happen if the terminals of the battery are reversed and the switch is closed? Explain.
3. Explain the two laws that help us understand this phenomenon.

The energy of a photon of wavelength 663 nm is ______.

With the help of a circuit diagram, explain how a full wave rectifier gives output rectified voltage corresponding to both halves of the input ac voltage.