ISC (Science) ISC Class 12 - CISCE Important Questions for Physics (Theory)

Explain why core of a transformer is always laminated.

State Moseley's law

To which regions of the electromagnetic spectrum do the following wavelengths belong: 
(a) 250 nm 
(b) 1500 nm 

Arrange the following electromagnetic waves in increasing order of their frequencies (i.e. begin with the lowest frequency):
Visible light, y rays, X rays, microwaves, radio waves, infrared radiations, and ultraviolet radiation.

Name the part of the electromagnetic spectrum which is: 
Suitable for radar systems used in aircraft navigation.

Name the part of the electromagnetic spectrum which is: 
Produced by bombarding a metal target with high electrons.

Calculate the shortest wavelength of electromagnetic radiation present in Balmer series of hydrogen spectrum.

Name the electromagnetic radiation whose frequency is 10 Hz.

What is the speed of radio waves in vacuum?

Name the electromagnetic radiation that has been used in obtaining the image below.

What is the wavelength range of electromagnetic radiation used in radio broadcast?

In an atom X, electrons absorb the energy from an external source. This energy “excites” the electrons from a lower-energy level to a higher-energy level around the nucleus of the atom. When electrons return to the ground state, they emit photons.

The figure below is the energy level diagram of atom X with three energy levels, E₁ = 0.00eV, E₂ = 1.78eV and E₃ = 2.95eV. The ground state is considered 0 eV for reference. The transition of electrons takes place between levels E₁ and E₂.

1. What wavelength of radiation is needed to excite the atom to energy level E₂ from E₁?
2. Suppose the external source has a power of 100 W. What would be the rate of photon emission?

Define critical angle for a given medium.

Name any two phenomena which take place in the formation of a rainbow.

The focal length of a double convex lens is equal to the radius of curvature of either surface. What is the refractive index of its material?