Nuclear Physics

Question 1

Alpha particles -

Answer 1

2 He 4
Charge = 2 * 1.6* 10^-19
Mass = 4 * 1.67 * 10^-27

Question 2

Discovery of nucleus -

Answer 2

By Rutherford (Alpha scattering experiment)

Question 3

Conclusion of Rutherford’s Alpha scattering experiment is:

Answer 3

An atom consists of a +ve nucleus at its center which consists of the entire +ve charge and the mass, which is known as nucleus.

Question 4

Size of atom and size of nucleus are in the order of ?

Answer 4

Size of atom - 10^-10 m
Size of nucleus - 10^-15 m

Question 5

What is impact parameter?

Answer 5

The perpendicular distance between the center of approaching alpha particle and the center of the nucleus is impact parameter.

Question 6

What is distance of closest approach?

Answer 6

The minimum distance between the center of the nucleus and the center of the approaching alpha - particle where kinetic energy of alpha particles reduces to zero and is repelled by the nucleus in the backward direction i.e. deflected by 180° is the distance of closest approach.

Question 7

Mass of nucleus is calculated by -

Answer 7

Mass of nucleus = Zmp + (A-Z)mn
Z = Atomic Number
A = Mass Number

Question 8

Formula for the size of nucleus is :

Answer 8

R = Ro A ^1/3
Where,
Ro = 1.2 * 10^-15 m OR 1.2 fm
A = Mass number
R = Radius of nucleus

Question 9

The density of all nucleus is approx. :

Answer 9

2.21 * 10^17 kg/m^3

Question 10

What are Isotopes?

Answer 10

Those nuclei which have same atomic number but different atomic mass are isotopes.

Question 11

What are Isobars?

Answer 11

Those nuclei having same atomic mass but different different atomic number are isobars. Example :
6 C 12 and 7 N 14

Question 12

What are isotones?

Answer 12

Those nuclei having same number of neutrons are isotones. Example :
11 Na 23 and 12 Mg 24

Question 13

What is atomic mass? (Not same as mass number)

Answer 13

The mass of neutral atom which includes mass of protons neutrons and mass of orbit electrons is atomic mass.

Question 14

Mass of proton, neutron and electrons are?

Answer 14

Proton - 1.672622 * 10^-27 kg
Neutron - 1.674927 * 10^-27 kg

Question 15

1ev =? J

Answer 15

1 ev = 1.6 * 10^-19 J
1 Mev = 1.6 * 10^-13 J

Question 16

1 amu = ? Mev

Answer 16

1 amu = 931 Mev

Question 17

Why is the mass sum of nucleons is greater than mass of nucleus?

Answer 17

• Some energy is released during formation of the nucleus and the mass decreases.

Question 18

What is binding energy?

Answer 18

The amount of energy released during formation of nucleus is BE or the amount of energy required to break up the nucleus into its constituents is BE.

Question 19

If mass defect is in amu, then

Answer 19

BE = Δm * 931 ( In Mev )

Question 20

If mass defect is in kilograms, then

Answer 20

BE = Δm * c^2

Question 21

What meaning does B.E./A give?

Answer 21

B.E./A gives amount of energy needed to remove a nucleon from its nucleus.

Question 22

What is nuclear reaction?

Answer 22

A reaction that involves the change in the nucleus of one element into the nuclei of other elements is known as nuclear reaction.

Question 23

What is Q-value of a reaction?

Answer 23

The energy released or absorbed during a nuclear reaction is Q-value of the reaction.

Question 24

If Q value of +ve -
If Q value of -ve -

Answer 24

Exothermic
Endothermic

Question 25

Q value is

Answer 25

( Mr -Mp ) * 931 Mev