388 7 Nuclear Physics – I
7.57 X-rays are Compton scattered at an angle of 60◦. If the wavelength of the
scattered radiation is 0.312A, find the wavelength of the incident radiation. ̊
7.58 Compare the energy loss of a photon in the following situations.
(a) One single Compton scattering through 180◦
(b) Two successive scatterings through 90◦each
(c) Three successive scatterings through 60◦each
7.59 For Aluminum, and a photon energy of 0.06 MeV, the atomic absorption cross-
section due to the Compton effect is 8. 1 × 10 −^24 cm^2 and due to the photo-
effect is 4. 0 × 10 −^24 cm^2. Calculate how much the intensity of a given beam
is reduced by 3.7gcm−^2 of aluminum and state the ratio of the intensities
absorbed due to the Compton effect and due to the photo effect.
[University of Bristol 1963]
7.60 Calculate the maximum change in the wavelength of Compton scattered
radiation.
7.61 A photon is Compton scattered off a stationary electron through an angle of
45 ◦and its final energy is half its initial energy. Calculate the value of the
initial energy in MeV
7.62 What is the range of energies of gamma rays from the annihilation radiation
which are Compton scattered?
7.2.5 Photoelectric Effect ................................
7.63 The wavelength of the photoelectric threshold for silver is 3,250× 10 −^10 m.
Determine the velocity of electron ejected from a silver surface by ultraviolet
light of wavelength 2,536× 10 −^10 m
[University of Durham 1960]
7.64 The gamma ray photon from^137 Cs when incident upon a piece of uranium
ejects photo-electrons from its K-shell. The momentum measured with a mag-
netic beta ray spectrometer, yields a value of Br= 3. 08 × 10 −^3 Wb/m. The
binding energy of a K-electron in Uranium is 115.59 keV. Determine
(a) the kinetic energy of the photoelectrons
(b) the energy of the gamma ray photons
[University of Durham 1962]
7.65 Ultraviolet light of wavelength 2,537A from a mercury arc falls upon a silver ̊
photocathode. If the photoelectric threshold wavelength for silver is 3,250A, ̊
calculate the least potential difference which must be applied between the
anode and the photo-cathode to prevent electrons from the photo-cathode.
[University of Durham]
7.66 Show that photoelectric effect can not take place with a free electron.