Question 259: Ray Optics

Question

A thin glass (refractive index $$1.5$$) lens has optical power of $$-5$$ $$D$$ in air. Its optical power in a liquid medium with refractive index $$1.6$$ will be

Accepted Answer

$${1 \over {{f_a}}} = \left( {{{1.5} \over 1} - 1} ight)\left( {{1 \over {{R_1}}} - {1 \over {{R_2}}}} ight)\,\,\,\,\,\,\,\,\,\,\,\,...\left( i ight)$$
$${1 \over {{f_m}}} = \left( {{{{\mu _g}} \over {{\mu _m}}} - 1} ight)\left( {{1 \over {{R_1}}} - {1 \over {{R_2}}}} ight)$$
$${1 \over {{f_m}}} = \left( {{{1.5} \over {1.6}} - 1} ight)\left( {{1 \over {{R_1}}} - {1 \over {{R_2}}}} ight)\,\,\,\,\,\,\,\,\,\,\,\,...\left( {ii} ight)$$
Dividing $$(i)$$ by $$(ii)$$, $${{{f_m}} \over {{f_a}}} = \left( {{{1.5 - 1} \over {{{1.5} \over {1.6}} - 1}}} ight) =  - 8$$
$${P_a} =  - 5 = {1 \over {{f_a}}} \Rightarrow {f_a} =  - {1 \over 5}$$
$$ \Rightarrow {f_m} =  - 8 	imes {f_a} =  - 8 	imes  - {1 \over 5} = {8 \over 5}$$
$${P_m} = {\mu  \over {{f_m}}} = {{1.6} \over 8} 	imes 5 = 1D$$

Answer

$$-1$$ $$D$$

Answer

$$1$$ $$D$$

Answer

$$-25$$ $$D$$

Answer

$$25$$ $$D$$

Ray Optics

A thin glass (refractive index $1.5) lens has optical power of -5 D in air. Its optical power in a liquid medium with refractive index 1.6$ will be

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