A wavelength of a 1 KeV photon is `1.2xx10^(-9)`m. What is the frequency of 1MeV photon ?

Options

A. `1.25xx10^(20)Hz`
B. `1.75xx10^(20)` Hz
C. `2.5xx10^(20)`Hz
D. `3.5xx10^(19)`Hz

Answer

C

Explanation

Frequency of 1 KeV photon is `v_(1)=(c)/(lambda_(1))=2.5xx10^(17)Hz`
Energy of a photon `E=hv`
`:. E_(2)=` Energy of 1 MeV photon `=10^(6)eV`
`E_(1)=` Energy of 1 KeV photon `= 10^(3) ` eV
`:. (E_(2))/(E_(1))=(hv_(2))/(hv_(1)) :. (v_(2))/(v_(1))= (10^(6))/(10^(3))=10^(3)`
`:.v_(2)=10^(3)v_(1)=10^(3)xx2.5xx10^(17)=2.5xx10^(20)Hz`