The radii of curavture of surfaces of a convex lens of glass are `20 cm` each. If `mu` is glass is `3//2`, power of lens in diopter is.

Answer

`5`

Explanation

Here, `R_(1) = 20 cm`,
`R_(2) = - 20 cm, mu = 3//2, P = ?`
`(1)/(f) = (mu - 1)((1)/(R_(1)) - (1)/(R_(2)))`
`= ((3)/(2) - 1) ((1)/(20) + (1)/(20)) = (1)/(20)`
`f = 20 cm`
`P = (100)/(f) = (100)/(20) = 5D`