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double-convex lensis tobemanufacturedfroma glassof refractive index1.55withbothfacesof the same radiusof curvatures . Calculatethe radiusofcurvaturerequiredif thefocallengthis tobe 20 cm ?Alsofind thefocallengthofthe lensif itis immersedin waterof refractiveindex 1.33 ? |
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Answer» Solution :given: `n_g =1.55 ,R = ? ,F=20cm, R_I = + R ,R_2 =- R ` `(1)/(f)=(n_g-1)[(1)/(R_1)-(1)/(R_2)]` `(1)/(20)= (1.55 -1) [1/R +1/R ]` `=0.55 xx2/R` `R=20xx 0.55 xx 2` ` R =22CM ` WHENTHE lensis IMMERSED in water `(1 )/(f_omega)=((n_g)/(n_omega)-1) [(1)/(R_1)-(1)/(R_2)]` `(1)/(f_(omega) )= ((1.55)/(1.33)-1)[(1)/(22)+(1)/(22)]` `(1)/(f_omega) =(1.1654 -1) 2/22` `(1)/(f_omega)= 0.1654 xx(2)/(22)` `(1)/(f_omega)=(0.3308)/(22)` `f_(omega)=(22)/(0.3308)` `f_(omega) = 66.5cm ` |
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