When light from one source, X, strikes a metal, electrons are ejected. When light from another source, Y, strikes the same metal, electrons are not ejected. Which best explains why this occurs?
Answer
A
Photons of light from source X carry less energy than photons of light from source Y.
B
Photons of light from source X carry more energy than photons of light from source Y.
C
Light from source X has a higher intensity than light from source Y.
D
Light from source X has a lower intensity than light from source Y.
Explanation
For electrons to be ejected, each photon must have enough energy to overcome the metal’s work function. Since source X ejects electrons and source Y does not, photons from X must carry more energy than photons from Y. The relevant factor is photon energy, not light intensity.
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