### Physics - Nuclear Physics and Radioactivity

#### Question - 1

The ratio of the nuclear radii of Cs135 to Ca40 is

• A 1.35
• B 3.375
• C 1.84
• D 1.5

#### Question - 2

Find the density of $^{12}_6C$ nucleus.

• A 2.7X10-17 kg/m3
• B 2.4X1017 kg/m3
• C 2.7X1015 kg/m3
• D 2.4X10-15 kg/m3

#### Question - 3

Assuming that all laws of thermodynamics can be applied to a nucleus, the $\alpha$-decay of a nucleus may be regarded as an

• A isothermal process
• B isobaric process
• D isochoric process

#### Question - 4

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

• A $^A_ZX+\gamma\rightarrow ^A_{Z-1}X+a+b$
• B $^A_ZX+^1_0n\rightarrow ^{A-3}_{Z-2}X+c$
• C $^A_ZX+^o_{-1}e\rightarrow ^A_{Z-1}X+g$
• D $^A_ZX^*\rightarrow ^A_{Z}X+f$

#### Question - 5

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

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

#### Question - 6

If one starts with one curie of radioactive substance (T1/2=12h), 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 - 7

A radioactive isotope X with a half-life of 1.37X109yr 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 1.96X108 yr
• B 3.85X109yr
• C 4.11X109yr
• D 9.59X109yr

#### Question - 8

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

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

#### Question - 9

The ratio of half-life and mean life of a radioactive sample is

• A ln 2
• B 1
• C $1\over ln \ 2$
• D $1\over 2\ ln \ 2$

#### Question - 10

From a newly formed radioactive substance (Half-life 2 h), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is

• A 6h
• B 12h
• C 24h
• D 128h