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A double concave lens with the refractive index{n} = 1.5 is kept in the air. If two spherical surfaces have Radii R1= 20cm and R2=60cm. Find the focal length of the lens.​

Answer 1

$\huge\boxed{ANSWER}$

we are given,

refractive index {n}=1.5

radii =20cm,60cm

as per lens makers formula ,

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

where f = focal length of lens

n= absoulte refractive index of lens

r1=radius of curvature 1

r2=radius of curvature 2

according to the question,

1/f=(1.5-1)(1/20-1/60)

=> 0.5 (-1/15)=-1/30

=> f = 30 cm

Answer 2

Answer:

Refer to the attachment for your answer.