Which of the following is used as a moderator in nuclear reactors? 

Heavy water is used as a moderator in a nuclear reactor. The function of the moderator is 

The binding energy per nucleon of deuterium and helium atom is 1.1 MeV and 7.0 MeV. If two deuterium nuclei fuse to form a helium atom, the energy released is 

In a fission reaction,

${}_{92}{}^{236}U\to {}_{117}X+{}_{117}Y+{}_0{}^{1}n+{}_0{}^{1}n$, the binding energy per nucleon of X and Y is 8.5 MeV whereas that of ${}_{236}U$ is 7.6 MeV. The total energy liberated will be about: [1997]

A nuclear decay is expressed as 

${}_{6}C_{11}\to {}_{5}B_{11}+{\beta }^{+}+X$

Then the unknown particle X is:

When a deuterium is bombarded on ${}_{8}O_{16}$ nucleus, an $\alpha$-particle is emitted, then the product nucleus is 

A nuclear reaction given by  ${}_{z}X_A\to {}_{z+1}Y_A+{}_{-1}e_0+\overline{\nu } represents$  [2003]

The mass of ${}_{7}N_{15}$ is 15.00011 amu, mass of ${}_{8}O_{16}$ is 15.99492 amu and $m_p$= 1.00783 amu. Determine binding energy of the last proton of ${}_{8}O_{16}$

The rate of disintegration of a fixed quantity of a radioactive substance can be increased by:

The energy released by the fission of one  uranium atom is 200 MeV. The number of fission per second required to produce 3.2 W of power is (Take, 1 eV = 1.6$\times$${10}^{-19} J$) [WB JEE 2010]

The power obtained in a reactor using $U^{235}$ disintegration is 1000 kW. The mass decay of $U^{235}$ per hour is:

Light energy emitted by stars is due to

The constituents of atomic nuclei are believed to be [1991]

The half-life of radium is about 1600 yr. Of 100 g of radium existing now, 25 g will remain unchanged after [2004]

Half-life of a radioactive substance is 12.5 h and its mass is 256 g. After what time, the amount of remaining substance is 1 g? [2001]

A radioactive substance disintegrates 1/64 of initial value in 60 s. The half-life of this substance is

The nucleus ${}_6{}^{12}C$ absorbs an energetic neutron and emits a beta particle $\left({\beta }^{-}\right)$. The resulting nucleus is 

If in a nuclear fusion  process, the masses of the fusion nuclei be $m_1 and m_2$ and the mass of the resultant nucleus be $m_3$, then [2004]

The nuclei of which one of the following pairs of nuclei are isotones? [2005]

The counting rate observed from a radio active source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed, as counts per second, at t = 6 seconds will be

If $N_0$ is the original mass of the substance of half life period $T_{1/2}$= 5 years, then the amount of substance left after 15 years is [AIEEE 2012]

The numbers of nuclei of a radioactive substance at time t = 0 are 1000 and 900 at time t = 2 sec. Then the number of nuclei at time t = 4 sec will be:

A nucleus ${}_Z{}^{A}X$ has mass represented by m(A, Z). If $m_p$ and $m_n$ denote the mass of proton and neutron respectively and BE is the binding energy (in MeV), then:
[2007]

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

Radioactive ${}_{27}{}^{60}Co$ is transformed into stable ${}_{28}{}^{60}Ni$ by emitting two $\gamma$-rays of energies

The volume occupied by an atom is greater than the volume of the nucleus by factor of about [2003]

A radioactive nucleus undergoes a series of decay according to the scheme 

$A\stackrel{\alpha }{\to }{A}_1\stackrel{\beta }{\to }{A}_2\stackrel{\alpha }{\to }{A}_3\stackrel{\gamma }{\to }{A}_4$

If the mass number and atomic number of A are 180 and 72 respectively, then what are these number for $A_4$?

What fraction of radioactive material will get disintegrated in a period of two half-lives?

If the nucleus ${}_{13}{}^{27}Al$ has a nuclear radius of about 3.6 fm, then ${}_{52}{}^{125}Te$ would have its radius approximately as [2007]

After two hours, one-sixteenth of the starting amount of a certain radioactive isotope remained undecayed. The half life of the isotope is [Bihar MEE 1995; Manipal MEE 1995; MP PMT 1997; AFMC 2000, 05; DPMT 2002]