In photoelectric effect, the work function of a metal is 3.5 eV. The emitted electrons can be stopped by applying a potential of - 1.2 V. Then
the energy of the incident photons is 4.7 eV
the energy of the incident photons is 2.3 eV.
if higher frequency photons be used, the photoelectric current will rise
when the energy of photos is 3.5 eV, the photoelectric current will be maximum
According to Einstein's photoelectric equation, the graph between the kinetic energy of photoeletrons ejected and the frequency of incident radiation 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
Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW. The number of photons arriving per second on the average at a target irradiated by this beam is
9 × 1017
3 × 1016
9 × 1015
3 × 1019
Which of the following is not the property of cathode rays ?
It produces heating effect
It does not deflect in electric field
Its casts shadow
It produces fluorescence
Einstein's work on photoelectric effect gives support to
E = mc2
E = hv
Which of the following is true ?
The stopping potential increases with increasing intensity of incident light
The photocurrent increases with increasing intensity of light
The current in photocell increases with increasing frequency of light
The photocurrent is proportional to applied voltage
The figure shows a plot of photocurrent versus anode potential for a photo sensitive surface for three different radiations. Which one of the following is a correct statement ?
Curves a and b represent incident radiations of different frequencies and different intensities
Curves a and b represent incident radiations of same frequency but of different intensities
Curves b and c represent incident radiations of different frequencies and different intensities
Curves b and c represent incident radiations of same frequency having same intensity
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
Gases begin to conduct electricity at low pressure because
at low pressures gases turn to plasma
colliding electrons can acquire higher kinetic energy due to increased mean free path leading to ionisation of atoms
atoms break up into electrons and protons
the electrons in atoms can move freely at low pressures
