Question

Blue light will not eject electrons from a certain metal. What should you do to find a type of EM radiation that will eject electrons? (Increase/decrease frequency?) Why do you need to change in this direction? Explain

Answer 1

The phenomenton behind this ejection of electrons is photo electric emission. In accordance with Photo electric effect, if a light of suitable frequency falls on smooth polished surface, electrons are ejected from the metal surface. The minumum frequency at which electrons are liberated called threshold frequency. Threshold frequency varies metal to metal.

In the given situation, blue light will not eject electrons from a certain metal, means the frequeny of blue light is not enogh to remove electron from metal surface. Thus, we have to increase the frequency towards violet , to metal surface liberate electrons.

Note: In visible spectrum, the frequency increases red to violet.

Here frequency corresponding to incidnet energy, E = hf; where E is energy, h is Plank's constant, and f is frequency.