COMEDK · Physics · 25. Ray Optics
A biconvex lens has two different refractive indices in different regions. The upper half has a refractive index 1.7 and the lower half has a refractive index 1.5 . The radius of curvatures of the two surfaces are \(R_1=15 \mathrm{~cm}\) and \(R_2=-25 \mathrm{~cm}\). Image of a distant object will be formed at:
- A 7.98 cm and 9.67 cm
- B 13.39 cm and 18.75 cm
- C 20.56 cm and 25.34 cm
- D 15.39 cm and 20.75 cm
Answer & Solution
Correct Answer
(B) 13.39 cm and 18.75 cm
Step-by-step Solution
Detailed explanation
The focal length \(f\) of a lens is given by the lens maker formula: \(\dfrac{1}{f} = (\mu - 1) \left( \dfrac{1}{R_1} - \dfrac{1}{R_2} \right)\). For the upper half, the refractive index \(\mu_1 = 1.7\). Given \(R_1 = 15 \text{ cm}\) and \(R_2 = -25 \text{ cm}\), the focal…
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