Given aμ g=3/2 and aμ w=4/3 . There is an equiconvex lens with radius of each surface equal to 20 cm. There is air in the object space and water in the image space. The focal length of lens is

Question

Given aμ g=3/2 and aμ w=4/3 . There is an equiconvex lens with radius of each surface equal to 20 cm. There is air in the object space and water in the image space. The focal length of lens is (A) 80 cm (B) 40 cm (C) 20 cm (D) 10 cm

Tardigrade Admin · Accepted Answer

(a μi/f)=((aa-1)/R1)-((μg-a μw)/R2) =(((3/2)-1)/20)-(((3/2)-(4/3))/-20) =(1/40)+(1/120)=(1/30) ∴ f=(4/3) × 30=40 cm

Q. Given $_{a} μ_{g} = 3/2$ and $_{a} μ_{w} = 4/3$ . There is an equiconvex lens with radius of each surface equal to $20 c m$ . There is air in the object space and water in the image space. The focal length of lens is

80 cm

40 cm

20 cm

10 cm

$\frac{a μ _{i}}{f} = \frac{( a _{a} - 1 )}{R _{1}} - \frac{( μ _{g} - a μ _{w} )}{R _{2}}$
$= \frac{( \frac{3}{2} - 1 )}{20} - \frac{( \frac{3}{2} - \frac{4}{3} )}{- 20}$
$= \frac{1}{40} + \frac{1}{120} = \frac{1}{30}$
$∴ f = \frac{4}{3} \times 30 = 40 c m$

Q. Given a​μg​=3/2 and a​μw​=4/3 . There is an equiconvex lens with radius of each surface equal to 20cm. There is air in the object space and water in the image space. The focal length of lens is