InterviewSolution
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InterviewSolution
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Obtain the equation of thin lens. |
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Answer» Solution :For refraction at two spherical surfaces of lens, `(n_1)/(-u)+(n_1)/(v)=(n_2-n_1)[(1)/(R_1)-(1)/(R_2)]` `therefore(1)/(-u)+(1)/(v)=((n_2)/(n_1)-1)[(1)/(R_1)-(1)/(R_2)]` [`therefore` DIVIDING by `n_1`] `therefore(1)/(-u)+(1)/(v)=(n_(21)-1)[(1)/(R_1)-(1)/(R_2)]` ... (1) and lens maker.s formula, `1/f=(n_(21)-1)[(1)/(R_1)-(1)/(R_2)]` ... (2) By comparing equation (1) and (2), `1/f=(1)/(-u)+(1)/(v)` or `1/f=1/v-1/u` Here, the DISTANCES are as per sign conventior and this equation is true for real and virtua images of convex and concave lenses. |
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