Question

Photons of energy 12eV are incident on a metal. It is found that current flows from the metal until a stopping potential of 8.0V is applied.



What would happen if the wavelength of the incident photons was tripled?

Would the energy be 4eV,so 12/3=4, and there will be no current flow? Is this correct? Please help!Thank you.

Answer 1

If the wavelength goes up, the frequency and therefore energy goes down by a factor of three. If that frequency is now below the threshold frequency required to free an outer electron from the metal, there will be no emission at all and no current no matter what intensity or stopping voltage.

Answer 2

Now those electrons had a Ke of 8 eV after being freed from the metal.
So 4 ev of the 12 was used just to spring the electrons out of their orbits.
If you only hit the metal with 4 eV photons, you just barely release the outer electrons and a tiny stopping voltage approaching zero will reduce the current to zero.

Answer 3

THANK YOU DAMON!