Work function of nickel is 5.01 eV. When ultraviolet radiation of wavelength `200A` is incident of it, electrons are emitted. What will be the maximum velocity of emitted electrons?

Options

A. `3xx10^(8) ms^(-1)`
B. `6.46xx10^(5)ms^(-1)`
C. `10.36xx10^(5) ms^(-1)`
D. `8.54xx10^(6) ms^(-1)`

Answer

B

Explanation

Energy corresponding to `2000 A=(12375)/(2000)eV=6.2eV`
Maximum kinetic energy is
`(6.2-5.01)eV=1.19eV`
Now, `(1)/(2)xx9.1xx10^(-31)xxv_(max)^2`
`=1.19xx1.6xx10^(-19)`
or `v_(max)^2=(1.19xx1.6xx10^(-19)xx2)/(9.1xx10^(-31))`
`=.0418xx10^(12)=41.8xx10^(10)`
or `v_(max)=6.46xx10^(5)ms^(-1)`