The work function for tungsten and sodium are `4.5 eV` and `2.3 eV` respectively . If the threshold wavelength `lambda` for sodium is `5460 Å`, the value of `lambda` for tungsten is

Options

A. `5893 Å`
B. `10683 Å`
C. `2791 Å`
D. `528 Å`

Answer

C

Explanation

Since `W_(0) = (hc )/(lambda_(0)), :. ((W_(0))_ T)/((W_(0))_(Na)) = (lambda_(Na))/(lambda_(T))` or
`lambda_(T) = ((lambda_(Na)) xx (W_(0))_(Na))/((W_(0))T) = ( 5460 xx 2.3)/(4.5) = 2791 Å`