A radiotransmitter operates at a frequency 1000 kHz and a power of 66 kW. Find the number of photons emitted per second.
1027
1028
1029
1030
Monochromatic light incident on a metal surface emits electrons with kinetic energies from 0 to 2.6 eV. What is the least energy of the incident photon, if the tightly bound electrons needs 4.2 eV to remove?
1.6 eV
Between 1.6 eV and 6.8 eV
6.8 eV
More than 6.8 eV
Which one of the following statements is wrong in the context of X-rays generated from an X-ray tube?
Wavelength of characteristic X-rays decreases when the atomic number of the target increases.
Cut-off wavelength of the continuous X-rays depends on the atomic number of the target.
Intensity of the characteristic X-rays depends on the electrical power given to the X-ray tube.
Cut-off wavelength of the continuous X-rays depends on the energy of the X-ray tube.
Einstein's work on photoelectric effect gives support to
E = mc2
E = hν
hν = 1/2 mv2
E = h/λ
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
Photon of frequency v has a momentum associated with it. If c is the velocity of light, the momentum is
v/c
hvc
hv/c2
hv/c
Light of wavelength 4000 angstrom is incident on a sodium surface for which the threshold wavelength of photoelectrons is 5420 angstrom. The work function is
4.58 electron volt
2.31 electron volt
1.14 electron volt
0.57 electron volt
When ultraviolet rays are incident on metal plate,the photoelectric effect does not occur.It occurs by incidence of
infrared rays
X -rays
radio waves
light waves
Bragg's equation will have no solution, if
λ > 2d
λ < 2d
λ < d
λ = d
If h is Planck's constant, the momentum of a photon of wavelength 0.01 Å is
h × 10-2
h
h × 102
h × 1012
