A convex lens of focal length 12 cm is made up of a glass of refractive index .When it is immersed in a liquid of refractive index , its focal length will be
15 cm
6 cm
30 cm
24 cm
When a p-n junction diode is connected to a battery with its p-side to positive terminal and n-side to negative terminal, the width of the depletion layer
decreases
increases
first decreases then increases
first increases then decreases
A.
decreases
When a p-n junction diode is connected to a battery with its p-side to positive terminal and n-side to negative terminal, the width of the depletion layer decreases and potential barrier is also decreases.
Wave nature of light does not explain
Interference
Total internal reflection
Photo-electric effect
Refraction
In forward and reverse biasing of a p-n junction diode, the ratio of resistances is
102 : 1
10-2 : 1
1 : 104
1 : 10-4
In a sample of radioactive substance, what percentage decays in one mean life time?
69.3 %
63 %
50 %
36 %
A p-type semiconductor is formed by adding 1 indium atom in to a sample of silicon per 5x10−7 silicon atoms. If the density of atoms in the sample is 5×1028 atoms/metre3, the number of atoms accepted in per metre3 of silicon is
1.0 × 1013 atoms/cm3
2.5 × 1020 atoms/cm3
2.5 × 1025 atoms/cm3
1.0 × 1015 atoms/cm3
The ratio of intensities of two waves is 1: 9. The waves interference, what will be the ratio of maximum and minimum intensities?
1:4
4:1
3:2
2:3
The light of frequency v falls on a certain photoelectric substance of threshold frequency v0. The work function of the substance is
hv0
hv
h(v - v0)
The magnification of an astronomical telescope is 10 and the focal length of eye-piece is 20 cm. The focal length of objective lens is
2 cm
200 cm
100 cm
A diver, at a depth of 12 metre from the surface of the water, sees the sky within a cone whose half vertex angle is :
cos−1
sin−1
90
sin−1