41.

If the energy released in the fission of one nucleus is 3.2x10^-11J, then number of nuclei required per second in a power plant of 16 kW is

• $0.5\times {10}^{14}$

• $0.5\times {10}^{12}$

• $5\times {10}^{12}$

• $5\times {10}^{14}$

If an electron has orbital angular momentum quantum number l =7 then it will have an orbital angular momentum equal to 

• $\sqrt{56}\left(\frac{\mathrm{h}}{2\mathrm{\pi }}\right)$

• $57\left(\frac{\mathrm{h}}{2\mathrm{\pi }}\right)$

• $42\left(\frac{\mathrm{h}}{2\mathrm{\pi }}\right)$

• $7\left(\frac{\mathrm{h}}{2\mathrm{\pi }}\right)$

The half-life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days?

• 0.0019 mg

• 1.019 mg

• 1.109 mg

• 0.019 mg

In the reaction given below ${}_{86}\mathrm{A}^{222} \to {}_{84}\mathrm{B}^{210}$. How many α and β particles are emitted?

• 6α, 3β

• 3α, 4β

• 4α, 3β

• 3α,6β

The phenomenon of radioactivity is :

• exothermic change which increases or decreases with  temperature

• increases on applied pressure

• nuclear process does not depend on external factors

• none of the above

In the reaction,${}_1{}^2\mathrm{H} +{}_1{}^3\mathrm{H} \to {}_2{}^4\mathrm{He} + {}_0{}^1\mathrm{n}$ if the binding energies of ${}_1{}^2\mathrm{H}, {}_1{}^3 \mathrm{H} \mathrm{and} {}_2{}^4\mathrm{He}$ are respectively a, b and c (in MeV), then the energy in this reaction is released in this reaction is

• c + a - b

• c - a - b

• a + b + c

• a +b - c

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

• $\frac{1}{2\mathrm{\lambda }}$