### NEET Physics - New - Nuclear Physics and Radioactivity

#### Question - 1

The ratio of the nuclear radii of  $\mathrm{Cs}^{135} \text { to } \mathrm{Ca}^{40}$ is

• A 1.35
• B 3.375
• C 1.84
• D 1.5

#### Question - 2

The ratio of radii of nuclei 13AI27 and 52XA is 3:5. The number of neutrons in the nuclei of X will be

• A 52
• B 73
• C 125
• D 13

#### Question - 3

Find the density of $\begin{array}{l} 12 \\ 6 \end{array}$C nucleus.

• A 2.7 x 10-17 kg/m3
• B 2.4 x 1017 kg/m3
• C 2.7 x 1015 kg/m3
• D 2.4 x 10-15 kg/m3

#### Question - 4

Which One of the following processes represents a $\gamma$-decay?

• A ${ }_Z^A X+\gamma \rightarrow{ }_{Z-1}^A X+a+b$
• B ${ }_Z^A X+{ }_0^1 n \rightarrow{ }_{Z-2}^{A-3} X+c$
• C ${ }_Z^A X+{ }_{-1}^0 e \rightarrow{ }_{Z-1}^A X+g$
• D ${ }_Z^A X^* \rightarrow{ }_Z^A X+f$

#### Question - 5

The half-life of 131 I is 8 day. Given a sample of 131I at time t= 0, we can assert that

• A no nucleus will decay before t= 4 day
• B no nucleus will decay before t=8 day
• C all nuclei will decay before t = 16 day
• D given nucleus may decay at any time after t= 0

#### Question - 6

A radioactive nucleus undergoes $\alpha$-emission to form a stable element. What will be the recoil velocity of the daughter nucleus, if v is the velocity of $\alpha$-emission and
A is the atomic mass of radioactive nucleus?

• A $\frac{4 v}{A-4}$
• B $\frac{2 v}{A-4}$
• C $\frac{4 v}{A+4}$
• D $\frac{2 v}{A+4}$

#### Question - 7

If one starts with one curie of radioactive substance (T1/2 = 12 h), then the activity left after a period of 1 week will be about

• A 1 curie
• B 120 micro curie
• C 60 micro curie
• D 8 mili curie

#### Question - 8

The half-life of radioactive radon is 3.8 day. The time at the end of which 1/20th of the radon samnple will remain undecayed is (Given, log10e = 0.4343)

• A 3.8 day
• B 16.5 day
• C 33 day
• D 76 day

#### Question - 9

A radioactive isotope X with a half-life of 1.37 x 109 yr decays to Y which is stable. A sample of rock from the moon was found to contain both the elements X and Y which were in the ratio of 1:7. The age of the rock is

• A 1.96 x 108 yr
• B 3.85 x 109 yr
• C 4.1l x 109 yr
• D 9.59 x 109 yr

#### Question - 10

A and B are two radioactive substances whose half-lives are 1 and 2 yr, respectively. Initially, 10 g of A and 1 g of B is taken. The time (approximate) after which they will have same quantity remaining is

• A 6.62 yr
• B 5 yr
• C 3.2 yr
• D 7 yr