Question

a bicnvex lens of radii 5 cm of 5 diopter power then what is the refractive index of the lens​

Answer 1

FORMULA

$\frac{1}{f} = (n - 1)( \frac{1}{r1} - \frac{1}{r2} )$

For a lens, power is given by 1/f. Hence, 1/f = P.

SOLUTION

Given,

P = 5

R= 5 cm.

For a biconvex lens , | R1 | = | R2 | .

Thus , R1 = 5 cm , R2 = - 5 cm.

putting in the formula :-

$5 = (n - 1)( \frac{1}{0.05} - \frac{1}{( - 0.05)}) \\ = > 5 = (n - 1)(40 )\\ = > \frac{1}{8} = n - 1 \\ = > n = \frac{9}{8}$

Hence, refractive index of the lens is 9/8.

==============================

More questions on geometrical optics :-

https://brainly.in/question/17247340

https://brainly.in/question/17173501

Answer 2

Answer:

Power lens,

P (in dioptre) = 100 / focal length f (in cm)

Therefore , f = 100 / 5 = 20 cm

So , the solution will be

According to lens maker's formula,

1/f = (μ - 1) [ (1/R₁) - (1/R₂) ]

For biconvex lens, R₁ = +R , R₂ = R

1/f = (μ - 1) [ (1/R) + (1/R) ]

1/f = (μ - 1) [ (2/R) ]

1/5 = (μ - 1) [ (2/5) ]

(μ - 1) = 1/2

μ = 1/2 + 1

μ = 3/2

The refractive index of the lens is 3/2