आइन्सटीन की पकाशवैधुत समीकरण से ,
` K_(max) = hv - phi_(0) = (hc)/lambda- (hc)/lambda_(0) `
` =hc [ 1/lambda - 1/(lambda_(0))] hc (lambda_(0)- lambda)/(lambda lambda_(0))`
, `lambda_(0) = 2890 Å = 2.89 xx 10^(-7)` मीटर
`(lambda_(0)-lambda)/(lambdalambda_(0)) = (2.89 xx 10^(-7) - 2.54 xx 10^(-7))/( 2.54 xx 10^(-7) xx 2.89 xx 10^(-7))/(2.54 xx 10^(-7) xx 2.89 xx 10^(-7))`
` = 4.786 xx 10^(5)`
` K_(max) = 6.6 xx 10^(-34) xx 3 xx10^(8) xx 4.768 xx 10^(5)`
= ` 9.44 xx 10^(-20)` जूल
(B) यदि निरोधी विभव `V_(0) "हो तो" , eV_(0) = K_(max) `
` V_(0) = (K_(max))/e = ( 9. 44 xx 10^(-20))/(1.6 xx 10^(-19)) = 0.6 ` वोल्ट