Unit of radioactivity is _____________

(a)

roentgen

(b)

curie

(c)

becquerel

(d)

all the above

_____________ aprons are used to protect us from gamma radiations

(a)

Lead oxide

(b)

Iron

(c)

Lead

(d)

Aluminium

In the nuclear reaction ₆X¹² \(\overset { \alpha \ decay }{ \longrightarrow } \) _zY^A, the value of A & Z.

(a)

8, 6

(b)

8, 4

(c)

4, 8

(d)

cannot be determined with the given data

Which of the following is/are correct?
i. Chain reaction takes place in a nuclear reactor and an atomic bomb.
ii. The chain reaction in a nuclear reactor is controlled
iii. The chain reaction in a nuclear reactor is not controlled
iv. No chain reaction takes place in an atom bomb

(a)

(i) only correct

(b)

(i) & (ii) are correct

(c)

(iv) only correct

(d)

(iii) & (iv) are correct

The explosion of the atomic bomb takes place due to

(a)

Nuclear fission

(b)

Nuclear fusion

(c)

Scattering

(d)

Heating

Fusion reaction takes place at high temp.

(a)

atoms are ionised

(b)

molecules break up

(c)

nuclei break up

(d)

to overcome repulsion between nuclei

Atomic nucleus was discovered by _______

(a)

Rutherford

(b)

Newton

(c)

Einstein

(d)

Nobel

Elements having atomic number greater than ________ are radioactive.

(a)

48

(b)

68

(c)

88

(d)

83

β-rays are nothing but _________.

(a)

protons

(b)

neutrons

(c)

electrons

(d)

helium

Radio ________ is used in the treatment of cancer.

(a)

sodium

(b)

cobalt

(c)

iron

(d)

phosphorous

Radio - carbon dating can be done with _________.

(a)

only living things

(b)

only non - living things

(c)

both (a) and (b)

(d)

none

Roentgen (R) is the unit to measure _________.

(a)

X - ray strength

(b)

number of holes produced by X - rays

(c)

radiation exposure

(d)

number of cancer cells

Radioactive materials are kept -in thick -walled ________ containers.

(a)

aluminium

(b)

iron

(c)

brick

(d)

lead

Minimum size of a system in which at least 1 neutron is available for further fission is called________.

(a)

cut - off size

(b)

critical size

(c)

range of reactor

(d)

capability criteria

Commonly used moderators are _________ and________.

(a)

D₂O, H₂O

(b)

D₂, H₂

(c)

O₂, H₂

(d)

O₂,N₂