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

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?

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.

A concave mirror of focal length 12 cm forms three times the magnified virtual image of an object. Find the distance of the object from the mirror.

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

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 ______.

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.

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

A converging lens has a focal length of 10 cm in air. It is made of a material with a refractive index of 1.6. If it is immersed in a liquid of refractive index 1.3, find its new focal length.

How is a wavefront different from a ray?

Explain the terms Attenuation used in Communication System.

Write three characteristic features in photoelectric effect that cannot be explained on the basis of wave theory of light, but can be explained only using Einstein's equation.

Sketch the graphs showing variation of stopping potential with frequency of incident radiations for two photosensitive materials A and B having threshold frequencies v_A > v_B.

(i) In which case is the stopping potential more and why?

(ii) Does the slope of the graph depend on the nature of the material used? Explain.

Ram is a student of class X in a village school. His uncle gifted him a bicycle with a dynamo fitted in it. He was very excited to get it. While cycling during night, he could light the bulb and see the objects on the road. He, however, did not know how this device works. he asked this question to his teacher. The teacher considered it an opportunity to explain the working to the whole class.

Answer the following questions:
(a) State the principle and working of a dynamo.

(b) Write two values each displayed by Ram and his school teacher.

Explain the terms : Transmitter in communication system

Light of intensity ‘I’ and frequency ‘v’ is incident on a photosensitive surface and causes photoelectric emission. What will be the effect on anode current when (i) the intensity of light is gradually increased. In each case, all other factors remain the same. Explain, giving justification in each case.