For a normal eye, the cornea of eye provides a converging power of 40 D and the least converging pow

Question

For a normal eye, the cornea of eye provides a converging power of 40 D and the least converging power of the eye lens behind the cornea is 20 D . Using this information, the distance between the retina and the cornea-eye lens can be estimated to be\

Professor PC Thomas Classes · Answer

(a) : Converging power of cornea, $P_{c}=+40 \mathrm{D}$ Least converging power of eye lens, $P_{e}=+20 \mathrm{D}$\ Power of the eye-lens, $P=P_{c}+P_{\mathrm{e}}$ $$ =40 \mathrm{D}+20 \mathrm{D}=60 \mathrm{D} $$ Power of the eye lens $$ P=\frac{1}{	ext { Focal length of the eye lens }(f)} $$ $$ f=\frac{1}{P}=\frac{1}{60 \mathrm{D}}=\frac{1}{60} \mathrm{~m}=\frac{100}{60} \mathrm{~cm}=\frac{5}{3} \mathrm{~cm} $$ Distance between the retina and cornea-eye lens = Focal length of the eye lens $$ =\frac{5}{3} \mathrm{~cm}=1.67 \mathrm{~cm} 	ag{i} $$