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The radius of curvature of each face of...

The radius of curvature of each face of biconcave lens, made of glass of refractive index 1.5 is 30 cm. Calculate the focal length of the lens in air.

Text Solution

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Here `n = 1.5 , R_(1) = - 30 cm , R_(2) = 3 cm`
Using len.s maker.s formula,
`(1)/(f) = (n-1)((1)/(R_(1))-(1)/(R_(2)))`
`=(1.5-1)[(1)/(-30)-(1)/(30)]=0.5xx((-2)/(30))`
`(1)/(f) = - (1)/(30)`
f = - 30 cm
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