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
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
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
Acceleration of an electron in the first Bohr orbit is proportional to
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
In the phenomenon of electric discharge through gases at low pressure,the coloured glow in the tube appears as a result of
excitation of electrons in the atoms
collision between the atoms of the gas
collisions between the charged particles emitted from the cathode and the atoms of the gas
collision between different electrons of the atoms of the gas
The de - Broglie wave corresponding to a particle of mass m and velocity v has a wavelength associated with it is
h/mν
hmν
mh/ν
m/hν
Three-fourths of the active nuclei present in a radioactive sample decay in 3/4 s. The half-life of the sample is
1 s
½ s
¾ s
3/8 s
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
