ISC (Science) ISC Class 12 - CISCE Question Bank Solutions

With what type of source of light are cylindrical wave fronts associated?

What is the geometrical shape of the wavefront for:

1. Light diverging from a point source?
2. The pattern of wavefront of the light from a distant star intercepted by earth?

Answer the following question briefly and to the point:

What is the phase difference between any two points lying on the same wavefront?

What type of wavefronts are associated with a source infinity?

Using Huygen’s wave theory of light, show that the angle of incidence is equal to the angle of reflection. Draw a neat and labelled diagram.

What type of wavefronts are associated with a point source of light?

Represent diagrammatically how the incident planar wavefronts of wavelength λ pass through an aperture of size d, when d is approximately equal to λ.

Represent diagrammatically how the incident planar wavefronts of wavelength λ pass through an aperture of size d, when d is approximately equal to λ.

An electrical bulb is marked 200V, 100W. Calculate the electrical resistance of its filament. If five such
bulbs are connected in series to a 200V supply, how much current will flow through them?

In a conductor 6.25 × `10^16` electrons flow from its end A to B in 2 s. Find the current flowing through the conductor (e = 1.6 × `10^-19` C)

What is meant by the drift speed of free electrons?

Explain the following term:

Intrinsic semiconductor

In Bohr’s model of the hydrogen atom, the radius of the first orbit of an electron is r₀ . Then, the radius of the third orbit is:

a) `r_0/9`

b) `r_0`

c) `3r_0`

d) `9r_0`

if `E_p` and `E_k` represent potential energy and kinetic energy respectively, of an orbital electron, then, according to B9hr's theory:

a)`E_k = -E_p"/"2`

b) `E_k = -E_p`

c) `E_k = -2E_p`

d) `E_k = 2E_p`

On the basis of Bohr's theory, derive an expression for the radius of the n^th orbit of an electron of the hydrogen atom.

State any two Bohr’s postulates and write the energy value of the ground state of the hydrogen atom. 

In which of the following systems will the wavelength corresponding to n = 2 to n = 1 be minimum?

According to Bohr, 'Angular momentum of an orbiting electron is quantized'. What is meant by this statement?

If l₃ and l₂ represent angular momenta of an orbiting electron in III and II Bohr orbits respectively, then l₃: l₂ is :

Calculate angular momentum of an electron in the third Bohr orbit of a hydrogen atom.