Question

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
A. is greater than zero but less than `1.5`
B. is greater thean `1.5` but less than `2.0`
C. is greater than one but less than `1.5`
D. none of these

Answer 1

Correct Answer - C
`(1)/(f)=(mu-1)((2)/(R))`or `f=(R)/(2(mu-1))`
Now, `fgtr`
`:. (R)/(2(mu-1))` or `(1)/(2(mu-1))gt1` or `2(mu-1)lt1`
or `mu-1lt(1)/(2)` or `mult(1+(1)/(2))` or ` mult1.5`