Question

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

Answer 1

Dear Student,

◆ Answer -

n = 3.4

● Explanation -

# Given -

R1 = 10 cm

R2 = 15 cm

f = 12 cm

# Solution -

Focal length of double convex lens is given as -

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

1/12 = (n-1) (1/10 - 1/15)

1/12 = (n-1) × 1/30

n - 1 = 30/12

n - 1 = 2.4

n = 3.4

Hence, refractive index of the material is 3.4.

Thanks dear. Hope this helps you...

Answer 2

Answer:

N=1.5

Explanation:

R1=10

R2=15

F=12

1/F=(n-1) (1/R1—1/R2)

Where R2 is always in hand side so it will be minus(—) and therefore

1/F=(n-1) (1/R1+1/R2)

1/12=(n-1) (1/10+1/15)

1/12=(n-1) (5/30)

1/12=(n-1) (1/6)

(n-1)=1/2

n=1+1/2

n=1.5

1.5

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