Question

The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm. If focal length is 12 cm. What is the refractive index of glass?

Answer 1

f = +12 cm ; R₁ = 10 cm ; R₂ = – 15 cm ; n = ?

As, \(\frac{1}{f}\) = = (n – 1) (\(\frac{1}{R_1}\) - \(\frac{1}{R_2}\))

\(\frac{1}{12}\) = (n-1) (\(\frac{1}{10}\) - \(\frac{1}{15}\)) = (n – 1) x \(\frac{5}{30}\)

(n – 1) = \(\frac{6}{12}\) = 0.5

n = 0.5 + 1

n = 0.5 +1

n = 1.5