# Atomic Physics

## Positronium is just like a H-atom with proton replaced by the positively charged anti-particle of the electron (called the positron which is as massive as the electron). What would be the ground state energy of positronium ?

Q: Positronium is just like a H-atom with proton replaced by the positively charged anti-particle of the electron (called the positron which is as massive as the electron). What would be the ground state energy of positronium ?

## Would the Bohr Formula for the H-atom remain unchanged if proton had a charge (+4/3)e and electron a charge (-3/4)e, where e = 1.6 × 10^-19 C. Give reasons for your answer.

Q: Would the Bohr Formula for the H-atom remain unchanged if proton had a charge (+4/3)e and electron a charge (-3/4)e, where e = 1.6 × 10-19 C. Give reasons for your answer.

## The simple Bohr model is not applicable to He^4 atom because

Q: The simple Bohr model is not applicable to He4 atom because

(a) He4 is an inert gas

(b) He4 has neutrons in the nucleus

(c) He4 has one more electron

(d) electrons are not subject to central forces

Ans: (c) & (d)

## Let E_n = (-me^4)/(8n^2 ε_0^2 h^2 ) be the energy of the nth level of H-atom. If all the H-atoms are in the ground state and radiation of frequency (E_2 – E_1 )/h falls on it,

Q: Let $E_n = -\frac{m e^4}{8 n^2 \epsilon_0^2 h^2}$ be the energy of the nth level of H-atom. If all the H-atoms are in the ground state and radiation of frequency $\frac{E_2 -E_1}{h}$ falls on it,

(a) it will not be absorbed at all

(b) some of atoms will move to the first excited state

(c) all atoms will be excited to the n = 2 state

(d) no atoms will make a transition to the n = 3 state

Ans: (b) & (d)

## The Bohr model for the spectra of a H-atom

Q: The Bohr model for the spectra of a H-atom

(a) will not be applicable to hydrogen in the molecular from

(b) will not be applicable as it is for a He-atom

(c) is valid only at room temperature

(d) predicts continuous as well as discrete spectral lines

Ans: (a) & (b)