Choose the correct alternative

Options

A. `K_(alpha)` wavelength emitted by an atom of atomic number `Z=21` is `lambda` then `K_(alpha)` wavelength emitted by an atom of atomic number `Z=31` is `(4 lambda)/(9)`
B. Half life of radioactive substance is `5` year, Probability that a nucleus decays in `10` years is `3//4`
C. Mass number of a nucleus is always greater than its atomic number
D. Gamma rays are emitted due to nuclear deexciation

Answer

A, B, D

Explanation

`(lambda_(1))/(lambda_(2))=(E_(2))/(E_(1))=((Z_(2)-a)^(2))/((Z_(1)-1)^(2))`