Consider an equiconvex lens of radius of curvature R and focal length f. If `fgtR` , the refractive index `mu` of the material of the lens

Options

A. is greater than zero but less than 1.5
B. is greater than 1.5 but less then 2.0
C. is greater than 1.0 but less than 1.5
D. None of these

Answer

c.

Explanation

`(1)/(f)=(mu-1)((2)/(R))`
or `f=(R)/(2(mu-1))`
Now, `f gt R`
`:. (R)/(2(mu-1)) gt R`
or ` (1)/(2(mu-1)) gt 1` or `2(mu-1) lt 1`
or `mu-1 lt (1)/(2)` or `mu lt (1+(1)/(2))` or `mu lt 1.5`