Light hits diode,causes current flow. Uses arc lamp.

Light hits diode, causes current flow. Uses arc lamp. (Similar to XX ) The P-N junction of a clear diode can act as a photoelectric source. The bright white light of a carbon arc is focused for a short time on a 1N34 diode. The current signal is displayed on a screen with a projection ammeter. (Note: focus light on the diode for only a brief time, or else the diode will be destroyed by overheating.) See Fig. 1. If light is shone on a PN junction, the light is absorbed, freeing electrons and creating holes. There is a strong electric field in the transition region between P and N, causing the electrons to move to the left and the holes to move to the right, causing a measurable current. Ref.:Modern College Physics by Harvey White, 6th ed., p. 600-601
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