Spectrum of sunlight is an example for

• continuous absorption spectrum

• band emission spectrum

• line absorption spectrum

• continuous emission spectrum

In hydrogen atom, electron excites from ground state to higher energy state and its orbital velocityis reduced to $\frac{1}{3}$rd of its initial value. The radius of the orbit in the ground state is R. The radius of the orbit in that higher energy

• 9 R

• 2 R

• 3 R

• 27 R

Decay constants of two radio-active samples A and B are 15x and 3x respectively. They have equal number of initial nuclei. The ratio of the number of nuclei left in A and B after a time $\frac{1}{6\mathrm{x}}$ is

• e^-2

• e

• e²

• e^-1

Mass number of the elements A, B, C and D are 30, 60, 90 and 120 respectively. The specific binding energy of them are 5 MeV, 8.5 MeV, 8 MeV and 7 MeV respectively. Then, in which of the following reaction/s energy is released ?

1.  D → 2B

2.  C → B + A

3.  B → 2A

• in (1), (2) and (3)

• Only in (1)

• in (2), (3)

• in (1), (3)

Copper and Germanium are cooled from room temperature to 100 K. Then, the resistance of

• germanium increases, copper increases

• germanium decreases, copper increases

• germanium decreases, copper decreases

• germanium increases, copper decreases

The most stable particle in the Baryon group is

• sigma particle

• neutron

• proton

• lambda particle

Frequencies of light incident on a system of scattering particles are in the ratio of 1 : 2. Then, the intensity of scattered light in a particular directions is

• 1 : 16

• 1 : 4

• 1 : 2

• 1 : 8

48.

The ratio of the magnetic dipole moment to the angular momentum of the electron in the 1st orbit of hydrogen atom is

• $\frac{\mathrm{m}}{\mathrm{e}}$

• $\frac{\mathrm{e}}{2\mathrm{m}}$

• $\frac{\mathrm{e}}{\mathrm{m}}$

• $\frac{2\mathrm{m}}{\mathrm{e}}$

White light is incident normally on a glass slab. Inside the glass slab

• all colours travel with the same speed

• red light travels faster than other colours

• violet light travels faster than other colours

• yellow light travels faster than other colours

Two thin plano-convex lenses each of focal length f are placed as shown in the figure. The ratio of their effective focal lengths in the three cases is

• 3 : 2 : 1

• 1 : 2 : 3

• 1 : 2 : 1

• 1 : 1 : 1