1.

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

Answer»

1
1.33
1.25
1.5

Solution :(d) `(1)/(f) = (n_(2) - 1) ((1)/(R_(1)) - (1)/(R_2))`
`(1)/(12) = (n_(2) - 1) ((1)/(10) - (1)/(=15))`
or `(1)/(12) = (n_(2) - 1) ((3+2))/(30) = ((n_(2) - 1))/(6)`
THUS, refractive index of glass, `n_(2) = 15`


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