Question

The photo-electric threshold wave length of a certain metal is 3000 $A^o$. If radiation of 2000 $A^o$ is incident on the metal

• A. Protons will be emitted
• B. Electrons will be emitted
• C. Positrons will be emitted
• D. Electrons will not be emitted

Answer 1

The correct option is B Electrons will be emitted

Threshold wavelength is 3000 $A^0$, and incident ray has wavelength of 2000 $A^0$. So, incident ray has less wavelength than the threshold wavelength. So, electrons will be emitted because at a threshold and less than threshold wavelength ejection of electrons takes place.
So, the answer is option (B).