Atomic and Nuclear Physics Answers

7. In the Helium-Neon laser, lasing occurs between two excited states of the neon atom. However, in many lasers lasing occurs between the ground state and an excited state. Consider

such a laser that emits at wavelength λ = 550 nm. If a population inversion is not generated,

(i) what is the ratio of the population of atoms in state Ex to the population in the ground

state E0 with atoms at room temperature? For the condition in (i), at (ii) what temperature

would the ratio Nx/N0 be 1/2?.

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.

Derive schrodinger equation

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?

2. (a) Compare or differentiate the Ruby Laser to the Helium Neon Laser with regard to their (i)

Gain medium (ii) Lasing wavelength (iii) uses. [3 marks]

(b) Consider the following nuclear reactions. Classify all the elementary particles involved and

tell (with a brief explanation) which of the three reactions is allowed / not allowed. [3 mark]

i. µ− −→ e− + νµ

ii. γ −→ e− + e+

iii. p + n̄ −→ π + π 0

(c) Briefly describe the basics principles of radiocarbon dating? [2 mark]

(d) Show that average lifetime (meanlife) of a radioactive nucleus is equivalent to Tm = λ1 , where

λ is the radioactive constant. [2 mar

Draw an energy-level diagram that shows the p levels with and without the external magnetic field.