Question

Sodium and copper have work function 2.3 eV and 4.5 eV respectively. Then, the ratio of the wavelengths is nearest to ______.

Options

• 4 : 1

• 1 : 4

• 2 : 1

• 1 : 2

Answer 1

Sodium and copper have work function 2.3 eV and 4.5 eV respectively. Then, the ratio of the wavelengths is nearest to 2 : 1.

Explanation:

Here, `omega_"Cu"` = 4.5 eV and `omega_"Na"` = 2.3 eV

Let λ_Cu and λ_Na be the corresponding wavelengths of these metals. Then,

`omega_"Cu" = "hc"/(lambda_"Cu") and omega_"Na" = "hc"/(lambda_"Na")`

or `omega_"Cu"/omega_"Na" = "hc"/(lambda_"Cu") xx (lambda_"Na")/"hc"`

or `(lambda_"Na")/(lambda_"Cu") = (omega_"Cu")/(omega_"Na") = 4.5/2.3 ~~ 2`