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 lt 40 kV`
B. `V le 40 kV`
C. `V gt 40 kV`
D. `V gt//lt40 kv`

Answer

C

Explanation

Applied voltage must be greater than binding energy.