The half-life period of a radio-active element X is same as the mean life-time of another radio-active element Y. Initially, they have the same number of atoms. Then

• X will decay faster than Y

• Y will decay faster than X

• X and Y have same decay rate initially

• X and Y decay at same rate always

If M₀ is the mass of an oxygen isotope ₈O¹⁷ , Mp and M_N are the masses of a proton and a neutron respectively, the nuclear binding energy of the isotope is

In gamma-ray emission from a nucleus

When ₃Li⁷ nuclei are bombarded by protons, and the resultant nuclei are ₄Be⁸ , the emitted particles will be

The ‘rad’ is the correct unit used to report the measurement of

A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 1 /2 m away, the number of electrons emitted by photocathode would