A and B are two metals with threshold frequencies 1.8 x 1014 Hz and 2.2 1014 Hz. Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted by (Take h = 6.6 x 10-34 J-s)
B alone
A alone
Neither A nor B
Both A and B
Electrons in a certain energy level n = n1 can emit 3 spectral lines. When they are in another energy level, n=n2 they can emit 6 spectral lines. The orbital speed of the electrons in the orbits are in the ratio
4 : 3
3 : 4
2 : 1
1 : 2
In Young's double-slit experiment with sodium vapor lamp of wavelength 589 nm and the slits 0.589 min apart, the half angular width of the central maximum is
sin-1(0.01)
sin-1(0.0001)
sin-1(0.001)
sin-1(0.1)
A radioactive element forms its own isotope after 3 consecutive disintegrations. The particles emitted are
3 β-particles
2 β-particles and 1α-particle
2 -βparticles and 1 γ-particle
2 α-particles and 1 β-particle
A radioactive substance contains 10000 nuclei and its half-life period is 20 days. The number of nuclei present at the end of 10 days is
7070
9000
8000
7500
The principle of LASER action involves
amplification of particular frequency emitted by the system
population inversion
stimulated emission
All of the above
A ray of light is traveling from glass to air, (refractive index of glass= 1.5). The angle of incidence is 50°. The deviation of the ray is
0°
80°
When the angle of incidence is 60° on the surface of a glass slab, it is found that the reflected ray is completely polarised. The velocity of light in glass is
√2 x 108 ms-1
√3 x 108 ms-1
2 x 108 ms-1
3 x 108 ms-1
In a reverse-biased diode when the applied voltage changes by 1 V, the current is found to change by 0.5 µA. The reverse bias resistance of the diode is
2 × 105 Ω
2 × 106 Ω
200 Ω
2 Ω
Through which mode of propagation, the radio waves can be sent from one place to another?
Ground wave propagation
Sky wave propagation
Space wave propagation
All of the above
D.
All of the above
Radio waves can be transmitted from one place to another as ground wave or skywave or space wave propagation.