Physics - Geometrical Optics Question with Solution | TestHub

The power of the convex lens is $P_1=\frac{1}{F_1}$

The power of the concave lens is $P_2=-\frac{1}{F_2}$

The power of the combined lens system is given by $P=P_1+P_2$

$P=\frac{1}{F_1}-\frac{1}{F_2}$

For the combination to behave as a concave lens, its effective power must be negative ($P<0$).

$\frac{1}{F_1}-\frac{1}{F_2}<0$

$\frac{1}{F_1}<\frac{1}{F_2}$

$F_1>F_2$

Answer: $F_1>F_2$