Two identical thin plano-convex glass lenses (refractive index = 1.5) each having radius of curvature of 20 cm are placed with their convex surfaces in contact at the center. The intervening space is filled with oil of refractive index 1.7. The focal length of the combination is - VgyanHub

Question:

Two identical thin plano-convex glass lenses (refractive index = 1.5) each having radius of curvature of 20 cm are placed with their convex surfaces in contact at the center. The intervening space is filled with oil of refractive index 1.7. The focal length of the combination is

Options :

(a) -25cm
(b) -50cm
(c) 50cm
(d) -20cm

Answer :

(b) -50cm

Answer Steps :

step 1

step 2

step 3

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