[" A convex lens has "20cm" focal "],[" length in air.What is the focal "],[" length in water? "],[48.2cm],[58.2cm],[68.2cm],[78.2cm]

A convex lens has 20 cm focal length in air.What is its focal length in water? (Refractive index of air-water is 1.33 , refractive index for air¬glass = 1.5).

(i) If f = 0.5 m for a glass lens, what is the power of the lens? (ii) The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm. Its focal length is 12 cm. What is the refractive index of glass? (iii) A convex lens has 20 cm focal length in air. What is focal length in water? (Refractive index of air-water = 1.33, refractive index for air-glass = 1.5.)

(i) If f = 0.5 m for a glass lens, what is the power of the lens? (ii) The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm. Its focal length is 12 cm. What is the refractive index of glass? (iii) A convex lens has 20 cm focal length in air. What is focal length in water? (Refractive index of air-water = 1.33, refractive index for air-glass = 1.5.)

A plano convex lens has focal length f = 20 cm . If its plane surface is silvered, then new focal length will be