SAT Subject Physics Practice Question 473: Answer and Explanation

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Question: 473


A light ray strikes a photovoltaic metal as shown above. Which of the following statements is correct if a voltage is introduced into the metal by the light ray?

I. The light ray is a blue light.

II. The beam is below threshold.

III. The beam does not contain any photons.

A. I only
B. II only
C. I and III only
D. II and III only
E. I, II, and III

Correct Answer: A


The correct answer is (A). We are told in the statement of the situation that a voltage is produced by photons striking the metal. This means the minimum threshold to meet the work function must have been met. This tells us the light is blue light, because the other two statements imply no voltage is produced in the metal.

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