Qn 1.

Spontaneous and continuous disintegration of a nucleus of a heavy element with the

emission of certain types of radiation is known as radioactivity.

a) The radioactive isotope ‘D’ decays according to the sequence

 

 

 

If the mass no. and atomic no. of D2 are 176 and 71 respectively, what is the

i) Mass number ii) atomic number of D

b) State radioactive decay law.

c) Distinguish between half-life and mean life of radioactive element. Write the relation connecting them.

Qn 2.

Nuclear fusion reaction is responsible for energy generation in stars.

a) What is the principle behind a nuclear reactor?

i) Fission

ii) Fusion

iii) Controlled fusion

 

b) Which of the following helps to slow down fast neutrons in a reactor?

i) Safety rods

ii) Moderator

 

c) In the nuclear reaction what is the element X?

 

 

 

d) The mass of an atom is expressed in......

i) Kg ii) g iii) u iv) Carats

Qn 3.

(a) what do you mean by Q value of a nuclear reaction?

(b) Write down the expression for Q value in the case of alpha decay.

(c) Two nuclei have mass numbers in the ratio 1:64. What is the ratio of their nuclear radii?

Qn 4.

a) Obtain an expression for the number of radioactive nuclei present at any instant in terms of the decay constant and initial number of nuclei.

(b) The half-life of radioactive radon is 3.8 days. Find the time during which 1/ 20 of

radon sample will remain undecayed.

Qn 5.

Suppose you are a health physicist and you are being consulted about a spill occured in a radiochemistry lab. The isotope spilled out in the lab was 500 micro cure of Ba 131 which has half life of 12-days.

a) what is the decay constant of Ba 131

b) What mass of Ba 131 was spilled

c) Your recommendation is to clear the lab untill the radiation level is down to 1 micro curie. How length will the lab have to be closed.