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if for a perfectly symmertical lens, r1=r2, then how will we find focal length??
Asked by Dark | 05 Jan, 2022, 11:54: AM
We have Lens maker's formula

............................... (1)
where f is focal length , μ is refractive index of materilal of lens , r1 is radius of curvature of left side
spherical surface and r2 is radius of curvature of right side spherical surface.

numerically r1 = r2 = r, by sign convention r1 is positive and r2 is negative .

Hence we get from eqn.(1)

From the known value of radius of curvature and refractive index of material ,
we get focal length f from above expression
Answered by Thiyagarajan K | 05 Jan, 2022, 01:22: PM

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