Four combinations of two thin lenses are given in List I. The radius of curvature of all curved surfaces is r and the refractive index of all the lenses is 1.5. Match lens combinations in List I with their focal length in List II and select the correct answer using the code given below the lists.

List I List II
A.
$P .$ $2 r$
B.
$Q .$ $\frac{r}{2}$
C.
$R .$ $- r$
D.
$S .$ $r$

Question

Four combinations of two thin lenses are given in List I. The radius of curvature of all curved surfaces is r and the refractive index of all the lenses is 1.5. Match lens combinations in List I with their focal length in List II and select the correct answer using the code given below the lists.

	List I		List II
A.		$P .$	$2 r$
B.		$Q .$	$\frac{r}{2}$
C.		$R .$	$- r$
D.		$S .$	$r$

Aicharya · Accepted Answer

1 f = 1 f 1 + 1 f 2 Use 1 f e q = 1 f 1 + 1 f 2 P 1 f e q = 1 R + 1 R = 2 R ; f e q = R 2 Q 1 f e q = 1 2 R + 1 2 R = 1 R ; f e q = R R 1 f e q = - 1 2 R - 1 2 R = - 1 R ; f e q = - R S 1 f e q = 1 R - 1 2 R = 1 2 R ; f e q = 2 R :

Four combinations of two thin lenses are given in List I. The radius of curvature of all curved surfaces is…

Solution