Question

A metallic surface ejects $n$ electrons per second when exposed to green color light of certain intensity I. The long wavelength limit for the surface being 560 nm. If the surface is exposed to the same intensity I of green, yellow and red light simultaneously, then the number of electrons emitted will be:

• A. n
• B. 2n
• C. 3n
• D. 9n

Answer 1

The correct option is A n

The long wavelength limit means the threshold wavelength.

• Lights of wavelength longer than that cannot emit electrons.
  
• If any such light falls on the surface, then it won't make any difference.
• Yellow and Red have wavelengths greater that green. Hence they are useless. Only green is useful.
• The number of electrons depends on the intensity of light.
• Since $Intensity$ of green is the same, the number of electrons emitted will be same.