Light of frequency `7.21xx10^(14)` Hz is incident on a metal surface .Electrons with a maximum speed of `6.0xx10^(5)m//s` are ejected from the surface .What is the threshold frequency for photoemission of electrons?

Explanation

Here frequency v`=7.21xx10^(14)` Hz
`v_(max)=6.0xx10^(5)m//s`
`V_(0)=?h=6.63xx10^(-34)Js`
`m=9.1xx10^(-31)Js`
`m=9.1xx10^(-31)kg`
`implies`From Einstien.s equation of photoelectric effect.
`K_(max)=hv-phi_(0)`
`therefore (1)/(2)mv^(2)max=hv-hv_(0)`
`thereforehv_(0)=hv-(1)/(2)mv^_(max)(2)`
`therefore v_(0)=v-(mv_(max)^(2))/(2h)`
`=7.21xx10^(14)-(9.1xx10^(-31)xx36xx10^(10))/(2xx6.63xx10^(-34))`
`=7.21xx10^(14)-2.47xx10^(14)`
`therefore v_(0)4.74xx10^(14) Hz`