JEE MAIN - Physics (2024 - 27th January Morning Shift - No. 14)
A convex lens of focal length $$40 \mathrm{~cm}$$ forms an image of an extended source of light on a photoelectric cell. A current I is produced. The lens is replaced by another convex lens having the same diameter but focal length $$20 \mathrm{~cm}$$. The photoelectric current now is :
$$\mathrm{\frac{I}{2}}$$
4 I
2 I
I
Vysvětlení
As amount of energy incident on cell is same so current will remain same.