Question

When I shine dim green light on a metal surface, no electrons are ejected.
Which of the following changes might cause electrons to be ejected from the surface?

• A. Shining bright green light on the metal surface
• B. Shining dim red light on the metal surface
• C. Shining dim purple light on the surface
• D. Shining bright red light on the metal surface
• E. Shining green light more directly on the metal surface

Answer 1

The correct option is A Shining bright green light on the metal surface

This is based on the photoelectric effect. More the intensity of the incident light(brighter the green light) more the no. of photo-electrons emitted . Dim light have low intensity such that it could not eject electrons from the metal surface.

Moreover using bright red light would have no effect. Because no. of photo-electrons emitted is independent of frequency and depends only on intensity of the light.