Problem set 53

1. Which one of the following axes of rotational symmetry is NOT permissible in single crystals?
1. two-fold axis
2. three-fold axis
3. four-fold axis
4. five-fold axis

The rotational symmetries of a crystal are usually limited to 2-fold, 3-fold, 4-fold, and 6-fold.

Hence, answer is (D)

2. Weak nuclear forces act on
1. both hadrons and leptons
2. hadrons only
3. all particles
4. all charged particles

Weak nuclear forces act on both hadrons and leptons, while strong nuclear force acts on hadrons only.

Hence, answer is (A)

3. Which one of the following disintegration series of the heavy elements will give $^{209}Bi$ as a stable nucleus?
1. Thorium series
2. Neptunium series
3. Uranium series
4. Actinium series

Uranium series terminates with lead-206

Actinium series terminates with lead-207

Thorium series terminates with lead-208

Neptunium series terminates with bismuth-209 and thallium-205

Hence, answer is (B)

4. The order of magnitude of the binding energy per nucleon in a nucleus is
1. $10^{-5}$ MeV
2. $10^{-3}$ MeV
3. 0.1 MeV
4. 10 MeV

Hence, answer is (D)

5. The interaction potential between two quarks, separated by a distance $r$ inside a nucleon, can be described by ($a$, $b$ and $\beta$ are positive constants)
1. $ae^{-\beta r}$
2. $\frac{a}{r}+br$
3. $-\frac{a}{r}+br$
4. $\frac{a}{r}$

The interaction potential between two quarks, separated by a distance $r$ inside a nucleon, can be described by $\frac{a}{r}+br$

Hence, answer is (B)