If voltage applied to `X` -ray tube increased from`V=10kV` to `20kV`. The wave length interval between `K_(alpha)-`line and short wave cut off continuous `X`-ray increases by factor of `3 (Rhc)/e=13.6V` where `R` is Rydberg constant `h` is plank's constant `c` is speed of light in vacuum and `e` is charge on electron

Options

A. Atomic no. of tangent metal used is `29`
B. Cut- off wavelength when `V=10kV` is `1.2Å`
C. Cut off wavelength when `V=10kV` is 2Å`
D. Atomic no. of target metal used is26

Answer

A

Explanation

Let `x` be the wave length for `K_(alpha)` line
`(x-(hc)/(eV_(2)))/(x-(hc)/(eV_(1)))=3`
`x=4/(3R(Z-1)^(2))`
`implies Z=29`