A 5 W source emits monochromatic light of wavelength 5000Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of
4
8
16
2
A light source is at a distance d from a photoelectric cell, then the number of photoelectrons emitted from the cell is n. If the distance of light source and cell is reduced to half, then the number of photoelectrons emitted will become
2n
4 n
n
A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of 3 × 106 ms-1 . The velocity of the particle is (mass of electron = 9.1 × 10-31 kg)
2.7 × 10-18 ms-1
9 × 10-2 ms-1
3 × 10-31 ms-1
2.7 × 10-21 ms-1
The number of photoelectrons emitted for light of a frequency v (higher than the threshold frequency v0 ) is proportional to
v - v0
threshold frequency (v0 )
intensity of light
frequency of light (v)
In a discharge tube ionisation of enclosed gas is produced due to collisions between
positive ions and neutral atoms/molecules
negative electrons and neutral atoms / molecules
photons and neutral atoms / molecules
neutral gas atoms / molecules
An electron moves with a velocity 1 ×103 m/s in a magnetic field of induction 0.3 T at an angle 30o. If of electron is 1.76 × 1011 C/kg, the radius of the path is nearly
10-8 m
2 × 10-8 m
10-6 m
10-10 m
The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of the incident radiation for which the stopping potential is 5 V lies in the
ultraviolet region
visible region
infrared region
X-ray region
An ionization chamber with parallel conducting plates as anode and cathode has 5 × 107 electrons and the same number of single charge positive ions per cm3. The electrons are moving towards the anode with velocity 0.4 m/s. The current density from anode to cathode is 4 μ A/m2. The velocity of positive ions moving towards cathode is
0.4 m/s
1.6 m/s
zero
0.1 m/s
Doubly ionised helium atoms and hydrogen ions are accelerated from rest through the same potential dop. The ratio of the final velocities of the helium and the hydrogen ion is
A photosensitive metallic surface has work function, hv0. If photons of energy 2 hv0 fall on this surface, the electrons come out with a maximum velocity of 4 × 106 m/s. When the photon energy is increased to 5 hv0, then maximum velocity of photoelectrons will be
2 × 106 m/s
2 × 107 m/s
8 × 105 m/s
8 × 106 m/s
