Wavelength of a `1 ke V` photon is `1.24 xx 10^(-9) m`. What is the frequency of ` 1 Me V` photon ?

Options

A. `1.24xx10^(15)Hz`
B. `2.4xx10^(20)Hz`
C. `1.24xx10^(18)Hz`
D. `2.4xx10^(23)Hz`

Answer

B

Explanation

Here, `lambda_(1)=1.24xx10^(-9)m, E_(1)=1KeV`,
`E_(2)=1MeV=10^(3)KeV, v_(2)=?`
As `E_(1)=hv_(1)` and `E_(2)=hv_(2) :. (E_(1))/(E_(2))=(v_(1))/(v_(2))`
`v_(2)=((E_(2))/(E_(1)))v_(1)=((E_(2))/(E_(1)))c/(lambda_(1))`
`=((10^(3)KeV)/(1KeV))xx(3xx10^(8))/(1.24xx10^(-9))`
`=10^(3)xx2.4xx10^(17)=2.4xx10^(20)Hz`.