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CBSE

NEET Physics : Nuclei

Multiple Choice Questions

191.

What is the particle X in the following nuclear reaction ?

${}_{4}^{9}{Be} + {}_{2}^{4}{He} \overset{}{\to} {}_{6}^{12}C + X$

Electron
Proton
Photon
Neutron

Short Answer Type

192.

At time t = O, a radioactive sample has a mass of 10 g. Calculate the expected mass of radioactive sample after two successive mean lives.

Multiple Choice Questions

193.

The energy released by the fission of one uranium atom is 200 MeV. The number of fissions per second required to produce 3.2 W of power is (Take, 1eV = 1.6 x 10^-19 J)

10⁷
10¹⁰
10¹⁵
10¹¹

Short Answer Type

194.

A radioactive isotope X with half life 1.5x 10⁹ yr decays into a stable nucleus Y. A rock sample contains both elements X and Y in ratio 1 : 15. Find the age of the rock.

Multiple Choice Questions

195.

A radioactive nucleus of mass number A, initially at rest, emits an α-particle with a speed v. The recoil speed of the daughter nucleus will be

$\frac{2 v}{A - 4}$
$\frac{2 v}{A + 4}$
$\frac{4 v}{A - 4}$
$\frac{4 v}{A + 4}$

196.

In the nuclear reaction ${}_{7}^{14}N + X \underset{}{\to} {}_{6}^{14}C + {}_{1}^{1}H$ , the X will be

${}_{- 1}^{0}e$
${}_{1}^{1}H$
${}_{1}^{2}H$
${}_{0}^{1}n$

197.

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 that of B will be (1/e)² after a time interval of

$\frac{1}{λ}$
$\frac{1}{2 λ}$
$\frac{1}{3 λ}$
$\frac{1}{4 λ}$

198.

The half-life of a radioactive isotope X is 20 yr. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio 1 : 7 in a sample of a given rock. The age of the rock is estimated to be

40 yr
60 yr
80 yr
100 yr

199.

A certain mass of hydrogen is changed to helium by the process of fusion. The mass defect in fusion reaction is 0.02866 u. The energy liberated per u is (given 1 u = 931 MeV)