Atomic and Nuclear Physics Answers

1. Using the Weiszacker’s formula, calculate the binding energy per nucleon for 235

92 U and

its two fission products: 149

60 Nd and 86

32Ge.

6. How much energy (in Joules) will be produced on complete fission of 1 kg of Uranium (235U), considering that only 0.1% of mass is converted into energy.

A large number of neon atoms are in thermal equilibrium. What is the ratio of the number of atoms in a 5s state to number in 3p state at (a) 300K; (b) 600K; (c) 1200K? The energy difference between two states is 1.96 eV. (d) at any of these temperatures, the rate at which a neon gas spontaneously emits 632.8nm radiation is quite low. Explain why? 

A large number of neon atoms are in thermal equilibrium. What is the ratio of the number of atoms in a 5s state to number in 3p state at (a) 300K; (b) 600K; (c) 1200K? The energy difference between two states is 1.96 eV. (d) at any of these temperatures, the rate at which a neon gas spontaneously emits 632.8nm radiation is quite low. Explain why?

What element is formed by the radioactive decay of (a) ( ) 24 11 − Na  ; (b) ( ) 22 11 + Na  ; (c) ( ) 210 15 P  ?

Natural magnesium occurs as a mixture of three isotopes: Mg 24 12 at 78,8%, Mg 25 12 at 10,1% and Mg 26 12 at 11,2%. Calculate the atomic mass of a natural sample of magnesium.

Two slits separated by 1.2 mm are placed 1.40 m from a screen. Light of wavelength 480 nm and 640 nm is incident on the slits. What is the separation distance on the screen of intensity maxima of the second order?

A narrow beam of 100 MeV neutrons, with a intensity 10 to the power 5

n/cm2

.s , is

normally incident on an aluminum foil. The elastic scattering cross

section of aluminum for 100 MeV neutrons is 0.95 barns. The density of

aluminum is 2.7 g/cm3

. How thick must the aluminum foil be in order to

reduce the number of unscattered neutrons emerging from the foil by

three orders of magnitude?

The sum of a number of proton and neutron is called:

A. Atomic number

B. Mass number

C. Isotopes

D. None of these

1. What is the number of a neutron in the nucleus of uranium:

A. 94

B. 145

C. 235

D. Same number

E. Different for different isotopes