The radii of curvature of the two surfaces of a lens are 20 cm and 30 cm and the refractive index of the material of the lens is 1.5. If the lens is c

Question

The radii of curvature of the two surfaces of a lens are 20 cm and 30 cm and the refractive index of the material of the lens is 1.5. If the lens is c

The radii of curvature of the two surfaces of a lens are 20 cm and 30 cm and the refractive index of the material of the lens is 1.5. If the lens is concave -convex, then the focal length of the lens is
A. 24 cm
B. 10 cm
C. 15 cm
D. 120 cm

Monjur Alahi

5 views

2025-01-04 04:42

1 Answers

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Salim Ahmed Kawsar · Accepted Answer · 2023-02-05T15:29:48+06:00

Salim Ahmed Kawsar

Correct Answer - D
(d) The focal length of the lens,
`1/f=(mu-1)(1/R_(1)-1/R_(2))`
`1/f=(1.5-1)(1/20-1/30)rArr1/f=0.5((30-20)/600)`
`or1/f=1/2xx10/600=1/120`
or The focal length, f = 120 cm

5 views Answered 2023-02-05 15:29