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

The work function of a metal is 2.31 eV. Photoelectric emission occurs when the light of frequency 6.4 × 10¹⁴ Hz is incident on the metal surface. Calculate

1. the energy of the incident radiation,
2. the maximum kinetic energy of the emitted electron and
3. the stopping potential of the surface.

The energy of hydrogen atom in an orbit is −1.51 eV. What are the kinetic and potential energies of the electron in this orbit?

The electron in a hydrogen atom is typically found at a distance of about 5.3 × 10⁻¹¹ m from the nucleus which has a diameter of about 1.0 × 10⁻¹⁵ m. Assuming the hydrogen atom to be a sphere of radius 5.3 × 10⁻¹¹ m, what fraction of its volume is occupied by the nucleus?

Give any two uses of infrared waves.

Draw an energy band diagram for a p-type semiconductor at T > 0 K.

How is the size of a nucleus found experimentally? Write the relation between the radius and mass number of a nucleus.

The radius of \[\ce{^27_13X}\] nucleus is R. The radius of \[\ce{^125_53Y}\] nucleus will be ______.

Which one of the following electromagnetic radiation has the least wavelength?

The ratio of the nuclear densities of two nuclei having mass numbers 64 and 125 is ______.

According to Huygens’s principle, the amplitude of secondary wavelets is ______.

Identify the electromagnetic wave whose wavelength range is from about 10^-12 m to about 10^-8 m. Write one use of this.

Identify the electromagnetic wave whose wavelength range is from about 10^-3 m to about 10^-1 m. Write one use of this.

Differentiate between the 'distance of the closest approach' and the 'impact parameter.'

Determine the distance of the closest approach when an alpha particle of kinetic energy 3.95 MeV approaches a nucleus of Z = 79, stops and reverses its directions.

Choose the correct option related to wavelengths (λ) of different parts of the electromagnetic spectrum.

Identify the electromagnetic radiation and write its wavelength range, which is used to kill germs in water purified. Name the two sources of these radiations.

When alpha particles are sent through a thin gold foil, most of them go straight through the foil, because ______.

Identify the part of the electromagnetic spectrum which:

1. produces the heating effect.
2. is absorbed by the ozone layer in the atmosphere.
3. is used for studying crystal structure.

Write any one method of the production of each of the above radiations.

How is a wavefront different from a ray?