# The capacitance of capacitors of plate area $A_2 and A_1 (A_2 < A_1)$ at a distance l is

$(A)\;\frac{\in _0 A_2}{l} \\ (B)\;\frac{\in _0A_1}{l} \\ (C)\; \frac{\in_0 \sqrt {A_1A_2}}{l} \\ (D)\;None$

Electric field between the two plates is perpendicular to surface of conductor as shown, therefore effective area is $A_2$
=> $C=\large\frac{\in _0 A_2}{l}$
Hence A is the correct answer.