A filter transition only the radiationof wavelength greater than 440 nm. Radiation from a hydrogen discharge tube goes through such a filter and is incident on a metel of work function 2.0eV . Find the stopping potential which can stop the photoelectrons.

Explanation

`lambda = 440 nm`
`theta =` Charge of the electron
`phi = 2eV`,
`v_0 =` Stopping potential.
We have (hc)/(lambda)-phi = eV_0`
implies `(4.14 xx 10^-15 xx 3 xx 10^8)/(440 xx 10^-9)-2eV = eV_0`
`eV_0 = (1242/440-2)eV =0.823 eV`.
implies `V_0 =0.823` Volts.