The intensity of X-rays from a coolidge tube is plotted against wavelength as shown in the figure . The minimum wavelegth found is `lambda_(c)` and the wavelength of the `K_(alpha)` line is `lambda_(k)`. As the accelerating voltage is increased

Options

A. `lambda_(K) - lambda_(C)` increases
B. `lambda_(K) - lambda_(C)`decreases
C. `lambda_(K)` increases
D. `lambda_(K)` increases

Answer

A

Explanation

In case of coolidge tube.
`lambda_(min) = (hc)/(eV) = lambda_(c )` (as given here)
Thus, the cut -off wavelength is inversely proportional to acclerating voltage. As `V` increases `lambda_(c )` decreases.
`lambda_(k)` is the wavelength of `K_(oo)` luine which is a characteristic of an atom and does not depond on accelerating voltage of bombarding electron since `lambda_(k)` always refers to a photon wavelength of transition of `e` from the target element from `2 to 1`
the above two facts lead to the conclusion that `lambda_(k)- lambda_( c)` increases as accelerating voltage is increased.