36.4.4a Curvature in 2-lens problem-I

Given two identical thin lenses, f₁ = f₂ = f. The object is located at distance p₁=2f from lens #1. Find curvature C_<2>

	1	2	3	4
C<2>	-1/f	-1/2f	1/f	1/2f

Hint: 1/p₁+1/q₁=1/f. Curvature C=±1/|R|. C₂ = 1/q₁.

Extra: Show C₃ =1/(q₁-d)=2/f. Use the curvature formula C₄=C₃+C_lens, show C₄=3/f, or q₂ = 0.33f.

Explanation: C_<2>=1/q₁= -1/p₁+1/f = -1/(2f) + 1/f = 1/(2f).

Extra: C₃=1/(q₁-d)=1/(2f - 1.5f) = 2/f.

C₄ = C₃+1/f = 1/(2f) + 1/f = 3/f = 1/q₂. q₂=0.33f.