The binding energy of the innermost electron in tungsten is `40 keV`. To produce characteristic `X` - rays using a tungsten target in an `X` - rays tube the potential difference `V` between the cathode and the anti - cathode should be

Options

A. `V ge 40` kV
B. `V lt 40` kV
C. `V gt 40` kV
D. `V le 40` kV

Answer

C

Explanation

B.E. = 40 keV
= 40,000 `xx 1.6 xx 10^(-19)` J
`q xx V = W = B.E`.
`e.V = 40 xx 10^(3) xx e`
V = 40 kV
Applied potential m ust be greater than 40 kV so th a t electron can eject from nucleus.