JEE Advanced · 2008 · 13 Apr 2008 · Paper 1 · Modern Physics

Which one of the following statements is WRONG in the context of X-rays generated from a X-ray tube?

(A)Wavelength of characteristic X-rays decreases when the atomic number of the target increases
(B)Cut-off wavelength of the continuous X-rays depends on the atomic number of the target✓ Correct
(C)Intensity of the characteristic X-rays depends on the electrical power given to the X-ray tube
(D)Cut-off wavelength of the continuous X-rays depends on the energy of the electrons in the X-ray tube

Answer: (B)

Solution

The cut-off wavelength of continuous X-rays is given by

λ_{cutoff} = \frac{h c}{e V}

, where

V

is the accelerating voltage. This depends only on the energy of the electrons (determined by

V

) and is independent of the atomic number of the target. Therefore, statement (B) is wrong.

JEE Advanced · 2008 · 13 Apr 2008 · Paper 1 · Single correct option