In the given nuclear reaction A, B, C, D, E represents
${}_{92}{}^{238}\mathrm{U}\stackrel{\mathrm{\alpha }}{\to }{}_{\mathrm{B}}{}^{\mathrm{A}}\mathrm{Th}\stackrel{\mathrm{\beta }}{\to }{}_{\mathrm{D}}{}^{\mathrm{C}}\mathrm{Pa}\stackrel{\mathrm{E}}{\to }{}_{92}{}^{234}\mathrm{U}$

(1) A = 234, B = 90, C = 234, D = 91, E = $\mathrm{\beta }$

(2) A = 234, B = 90, C = 238, D = 94, E =$\mathrm{\alpha }$

(3) A = 238, B = 93, C = 234, D = 91, E = $\mathrm{\beta }$

(4) A = 234, B = 90, C = 234, D = 93, E = $\mathrm{\alpha }$

In the disintegration series ${}_{92}{}^{238}\mathrm{U}\stackrel{\mathrm{\alpha }}{\to }\mathrm{X}\stackrel{\mathrm{\beta }-}{\to }{}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{Y}$ the values of Z and A respectively will be 

(1) 92, 236               

(2) 88, 230

(3) 90, 234               

(4) 91, 234

If half life of a radioactive element is 3 hours, after 9 hours its activity becomes 

(1) 1/9                     

(2) 1/27

(3) 1/6                     

(4) 1/8

Carbon-14 decays with half-life of about 5,800 years. In a sample of bone, the ratio of carbon-14 to carbon-12 is found to be $\frac{1}{4}$ of what it is in free air. This bone may belong to a period about x centuries ago, where x is nearest to 

(1) 2$\times$58                       

(2) 58

(3) 58/2                         

(4) 3$\times$58

Half life of a radioactive element is 10 days. The time during which quantity remains 1/10 of initial mass will be

(1) 100 days             

(2) 50 days

(3) 33 days               

(4) 16 days

The half life of ${}_{131}\mathrm{I}$ is 8 days. Given a sample of ${}_{131}\mathrm{I}$ at time t = 0, we can assert that 
(1) No nucleus will decay before t = 4 days

(2) No nucleus will decay before t = 8 days

(3) All nuclei will decay before t = 16 days

(4) A given nucleus may decay at any time after t = 0

At any instant the ratio of the amount of radioactive substances is 2 : 1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances?

(1) 1 : 1                 

(2) 2 : 1

(3) 1 : 2                 

(4) 1 : 4

Which of the following is a correct statement

(1) Beta rays are same as cathode rays

(2) Gamma rays are high energy neutrons

(3) Alpha particles are singly ionized helium atoms

(4) Protons and neutrons have exactly the same mass

The particles emitted by radioactive decay are deflected by magnetic field. The particles will be

(1) Protons and $\mathrm{\alpha }$-particles

(2) Electrons, protons and $\mathrm{\alpha }$-particles

(3) Electrons, protons and neutrons

(4) Electrons and $\mathrm{\alpha }$-particles