Question

a convex lens of focal length 20cm and radius of curvatures r1=30cm and r2=40cm.find mue

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Answer 1

Answer:

Let the radius of curvature of the convex lens are denoted as

For a convex lens  [As it is towards right]

                              [As it is towards left]

The refractive index of the lens  

Let f is the focal length of the lens.

From lens maker's formula we know that -

                               

                               

                               

                               

                                     [ans]

Hence, the focal length of the lens is 40 cm.

Answer 2

Answer:7

Step-by-step explanation:By formula,

1/f=(n-1)(1/R1-1/R2)

f=20cm

R1=30cm

R2=40cm

1/20=(n-1)(1/30-1/40)

1/20=(n-1)(4-3 /120)

1/20=(n-1)(1/120)

Which gives,

6=n-1

n=7