nuclear physics

Question 1

Which of the following is the percentage of the original quantity of a radioactive material left after five half-lives approximately

Answer 1

3%
Fraction undecayed after 5 half-lives = (½)5 = 1/32
% = 1/32 × 100 = 3%

Question 2

Principle of Hydrogen bomb in reactions.

Answer 2

Uncontrolled Fusion

Question 3

The half-life of Uranium-238 is?

Answer 3

4.5 × 10 9 years
Half-life of U-238 is much higher than U-239. Half-life of U-239 is 23.5 minutes. That is why most of the naturally occurring uranium (99%) is U-238.

Question 4

A source initially contains N0 nuclei of a radioactive nuclide. How many of these nuclei have decayed after a time interval of three half-lives?

Answer 4

7N0/8

Question 5

One curie is approximately equal to the number of α-particles emitted from a radium of mass

Answer 5

1 gm
It was originally defined as ‘the quantity or mass of radium emanation in equilibrium with one gram of radium

Question 6

Cobalt is absorbed in a whole body system by

Answer 6

the liver has natural ability to absorb cobalt

Question 7

The necessary condition for nuclear fusion is

Answer 7

High temperature and high pressure
High temperature – The high temperature gives the hydrogen atoms enough energy to overcome the electrical repulsion between the protons.
High pressure – Pressure squeezes the hydrogen atoms together. They must be within 1 × 10-15 meters of each other to fuse.

Question 8

if the half-life of an element is 10 second, the mean life will be:

Answer 8

14.4 sec
Tmean = 1.44T1/2

Question 9

Half-life of radium-226 is:

Answer 9

1620 years

Question 10

In Geiger counter:

Answer 10

The metal tube acts as the cathode and wire acts as the anode

Question 11

Decay constant “λ” given by:

Answer 11

–(ΔN/N)/Δt

Question 12

During fission process, the average number of neutrons emitted are:

Answer 12

2.5
Fission also results in the production of several neutrons, typically two or three. On the average, about 2.5 neutrons are released per unit and the energy of a neutron released per fission of a uranium atom are 2MeV.

Question 13

Nuclear weak force is experienced during:

Answer 13

only beta decay

Question 14

The most useful tracer is:

Answer 14

C – 14

Question 15

The relation between the disintegration constant “λ” and the half-life T of a radioactive substance is:

Answer 15

λT = ln2
λT1/2 = ln2
λT1/2 = 0.693
T1/2 = 0.693/λ

Question 16

Which of the following have no mass.

1. A. Leptons
2. B. Hydrons
3. C. Bosons
4. D. Meuons

Answer 16

Bosons are particles having no rest mass and no charge.

Question 17

Radiation damage to living organism is primarily due to…

Answer 17

Ionization
Ionizing radiation is the most harmful because it can ionize molecules or break chemical bonds, which damages the molecule and causes malfunctions in cell processes.

Question 18

According to Bohr model one of the following is a discrete quantity

Answer 18

angular momentum
nh/2π

Question 19

Slope of the decayed atoms vs the time is a isothermal curve as shown below, the slope/ gradient of this slope represents

Answer 19

Activity = No/t = slope of graph

Question 20

what is radius and energy directly proportional to?

Answer 20

Radius is directly proportional to square of number of orbit.
Energy is directly proportional to square of charge number.

Question 21

how to calculate avg life time w t1/2

Answer 21

T1/2 / 0.693
avg lifetime is 1/decay constant

Question 22

circulation of blood could be studied by radioactive isotope

Answer 22

Na - 24

Question 23

the rate of decay of radiactive substance —— with time

Answer 23

decreases

Question 24

what are isotones

Answer 24

diff elements having same neutron number, but diff nucleon number

Question 25

the path of beta particle is

Answer 25

erratic / zigzag

Question 26

fluorescence is the property of

Answer 26

visible light

Question 27

range of alpha particles

Answer 27

5 mm - 200 mm

Question 28

which force has negligible effect on elementary particles

Answer 28

gravitational force

Question 29

which of the following basic forces is able to provide an attraction between 2 neutrons

Answer 29

gravitational and strong nuclear
As nuclear force is responsible for binding protons and neutrons into atomic nuclei. So, it will provide attractive force between two neutrons. As neutron is a neutral particle so gravitational force will response.

Question 30

which type of dose is more reliable for describing the adverse effect of radiations on biological organisms

Answer 30

equivalent dose

Question 31

rest mass of electron is

Answer 31

9.1 x 10^-31