An equiconvex lens is cut into two halves along (i) XOX'

An equiconvex lens is cut into two halves along (i) XOX' and (ii) YOY' as shown in the figure. Let f, f ', f '' be the focal lengths of the complete lens, of each half in case (i), and of each half in case (ii), respectively.

Choose the correct statement from the following

1. f ' = 2f, f '' = 2f
2. f ' = f, f '' = 2f
3. f ' = 2f, f '' = f
4. f ' = f, f '' = f

	1	= (μ - 1)		1	-	1
	f			R₁		R₂

In this case, R₁ and R₂ are unchanged
So, f will remain unchanged for both pieces of the lens
∴ f = f '

	1	=	1	+	1
	f		f₁		f₂

This is combination of two lenses of equal focal lengths

∴	1	=	1	+	1	=	2	⇒ f" = 2f
	f		f"		f"		f"