161.

Radioactive decay will occur as follows

$$\begin{gathered} {}_{86}{}^{220}\mathrm{Rn} \stackrel{ }{\to } {}_{84}{}^{216}\mathrm{PO} + {}_2{}^4\mathrm{He} \mathrm{Half} \mathrm{life} = 55\mathrm{s} \\ {}_{84}{}^{216}\mathrm{PO} \stackrel{ }{\to } {}_{82}{}^{212}\mathrm{Pb} + {}_2{}^4\mathrm{He} \mathrm{Half} \mathrm{life} = 0.66 \mathrm{s} \\ {}_{82}{}^{812}\mathrm{Pb} \stackrel{ }{\to } {}_{82}{}^{212}\mathrm{BL} + \mathrm{\lambda }°\mathrm{e} \mathrm{Half} \mathrm{life} = 10.6 \mathrm{h} \end{gathered}$$

If a certain mass of radon (Rn = 220) is allowed to decay in a certain container; then after 5 minutes the element with the greater mass will be

• radon

• polonium

• lead

• bismuth

A nucleus ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}$ has mass represented by m (A,Z). If m_p and m_n denote the mass of proton and neutron respectively and BE the binding energy (in MeV) then.

• $\mathrm{BE} = \left[\mathrm{m}\right(\mathrm{A},\mathrm{Z}) - {\mathrm{Zm}}_{\mathrm{p}} - (\mathrm{A}-\mathrm{Z}\left){\mathrm{m}}_{\mathrm{n}}\right]{\mathrm{C}}^2$

• $\mathrm{BE} = [{\mathrm{Zm}}_{\mathrm{p}} + (\mathrm{A} -\mathrm{Z}){\mathrm{m}}_{\mathrm{n}} - \mathrm{m}(\mathrm{A},\mathrm{Z}\left)\right]{\mathrm{c}}^2$

• $\mathrm{BE} = [{\mathrm{Zm}}_{\mathrm{p}} + {\mathrm{Am}}_{\mathrm{n}} - \mathrm{m} (\mathrm{A},\mathrm{Z}\left)\right]{\mathrm{c}}^2$

• $\mathrm{BE} = \mathrm{m} (\mathrm{A},\mathrm{Z}) - {\mathrm{Zm}}_{\mathrm{p}} - (\mathrm{A}-\mathrm{Z}) {\mathrm{m}}_{\mathrm{N}}$

The half-life period of a radioactive element X is the same as the mean life of another radioactive element Y. Initially, both of them have the same numbers of atoms then,

• X and Y have the same decay rate initially

• X and Y decay at the same rate always

• Y will decay at a faster rate than X

• X will decay at a faster rate than Y

The mass of a proton is 1847 times that of an electron. An electron and a proton are injected into a uniform electric field at right angle to the direction of the field with the same initial K.E.

• The electron trajectory will be less curved than the proton trajectory.

• both the trajectories will be straight

• the proton trajectory will be less curved than the electron trajectory.

• both the trajectories will be equally curved.

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