Question

Fill in the blanks:
When light falls on the junction of a photo diode , the number of charge carriers _________ and hence the conductivity of the junction ________.

• A. increases, decreases
• B. decreases, increases
• C. decreases, decreases
• D. increases, increases

Answer 1

The correct option is D increases, increases

When light , above a certain frequency, is incident on the junction of a photo diode (operating in reverse bias), the width of the depletion layer increases. The electrons in the depletion, absorb the photon and come out from bond thus creating a electron-hole pair. Hence, the number of charge carriers increases and due to these charge carriers, conductivity of the junction also increases.