Fission of nuclei is possible because the binding energy per nucleon in them

• increases with mass number at high mass numbers

• decreases with mass number at high mass numbers

• increases with mass number at low mass numbers 

• decreases with mass number at low mass numbers

In any fission process the ratio $\underset{\mathrm{Mass} \mathrm{of} \mathrm{parent} \mathrm{nucleus}}{\overset{\mathrm{Mass} \mathrm{of} \mathrm{fission} \mathrm{products}}{\to }}$ is

• less than 1

• greater than 1

• greater than 1

• depends on the mass of parent nucleus

In radioactive decay process, the negatively charged emitted -particles are 

• the electrons present inside the nucleus

• the electrons produced as a result of the decay of neutrons inside the nucleus

• the electrons produced as a result of collisions between atoms

• the electrons orbiting around the nucleus

Two radioactive substances A and B have decay constants 5 λ and λ respectively. At t = 0 they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be ${\left(\frac{1}{\mathrm{e}}\right)}^2$ after a time interval

• $\frac{1}{4\mathrm{\lambda }}$

• 4λ

• 2λ

• $\frac{1}{2\mathrm{\lambda }}$

If M_o is the mass of an oxygen isotope ₈O¹⁷ , M_P and M_n are the masses of a proton and a neutron, respectively, the nuclear binding energy of the isotope is

• ( M_o - 8 M_P ) c² 

• ( M_o - 8 M_P - 9 M_c ) c²

• M_o C²

• (M_o - 17 M_n ) c²

Hydrogen bomb is based upon

• fission

• fusion

• chemical reaction

• transmutation

177.

The operation of a nuclear reactor is said to be critical, if the multiplication factor (k) has a value

• 1

• 1.5

• 2.1

• 2.5

Half-lives of two radioactive substances A and B are respectively 20 min and 40 min. Initially the samples of A and B have equal number of nuclei. After 80 min the ratio of remaining number of A and B nuclei is

• 1 : 16

• 4 : 1

• 1 : 4

• 1 : 1

The half-life of a radio-isotope is 4h. If initial mass of the isotope was 200 g, then mass remaining after 24 h will be

• 1.042 g

• 2.084 g

• 3.125 g

• 4.167 g

If ₈₂U²³⁸ emits 8 $\mathrm{\alpha }$ - particles and 6 β - particles, then the resulting nucleus is

• ₈₂U²⁰⁶

• ₈₂Pb²⁰⁶

• ₈₂U²¹⁰

• ₈₂U²¹⁴