write the basic assumptions used in the derivation of lens maker formula and hence derive this expression
Answers
Explanation:
Basic assumptions in derivation of Lens-maker’s formula: (i) Aperture of lens should be small (ii) Lenses should be thin (iii)Object should be point sized and placed on principal axis. Suppose we have a thin lens of material of refractive index n2, placed in a medium of refractive index n1, let o be a point object placed on principle axis then for refraction at surface ABC we get image at I1 , ∴ (n2/v2) - (n1/u) = (n2 - n1 )/ R1 ....(1) But the refracted ray before goes to meet at I1 falls on surface ADC and refracts at I2 finally; hence I1 works as a virtual object 2nd refracting surface ∴ n1/v - n2/v1 = (n1 - n2)/R2 ....(2) Equation (1) + (2) If u = ∞, ѵ = f Which is lens maker’s formulaRead more on Sarthaks.com - https://www.sarthaks.com/506038/write-basic-assumptions-used-derivation-lens-makers-formula-hence-derive-this-expression