Find out the kinetic energy of an electron whose de - Broglie wave length is `4000 overset(@) (A)`.

The threshold wavelength for a photosensitive metal is 3600 overset(@)(A) . Find the maximum kinetic energy of the ejected photoelectrons when light of 3000 overset(@) (A) incidents on the photosensitive surface. (Given , c = 3 xx 108 m//sec, h = 6.62 xx 10 ^- 34 JS)~