Question

The figure illustrates qualitatively a corrective lens of -2.75 diopters. R 8.46 cm The lens material is CR-39 monomer, with an index of refraction of 1.499. Calculate R, the radius of curvature of the outer surface for the lens. Note: the diopter is a measure of the refractive power of a lens, and equals the reciprocal of the focal length in meters. (Example: for +3 diopters, f=0.333 meters.) -18.54 cm Submit Answer Incorrect. Tries 4/12 Previous Tries

Answer 1

Answer:

Given, the lens has a lens power is -2.75 diopters

The relation between the focal length and Diopter is

focal length in mm = 1000/-2.75 = -363.63 mm = -36.36 cm

Using len's maker formula,

1/f = (n - 1) [1/R₁ - 1/R₂]

Given that R₁ = 8.46 cm

1/f = (n - 1)/R₁ - (n -1)/R₂

or (n -1)/R₂ = (1/f) + (n - 1)/R₁

or (1.499 -1)/R₂ = (1/-36.36 cm) + (1.499-1)/(8.46 cm)

or (1.499 -1)/R₂ = 0.0314 cm^-1

Therefore, R₂ = (0.499/ 0.0314) cm = 15.89 cm

Hence, this is the radius of curvature of the outer surface.