Two lenses (1) and (2) with `R_(1) = R_(2) = 0.20 m` each are made from glasses with `mu_(1) = 1.2 and mu_(2)` = 1.6 respectively. The two lenses with a separation of 0.345 m are submerged in a liquid with `mu_(1) = 1.4`. The focal lenghts of (1) and (2) are found. An object is placed at a distance of 1.3m from lens 1.
The focal lenght of 2 is :

Options

A. `- 700 cm`
B. ` + 700 cm`
C. 7 cm
D. 70 cm

Answer

D

Explanation

(d) `(1)/(f_(2)) = (.^(l)mu_(g)-1) ((1)/(R_(1)) - (1)/(R_(2)))`
`mu_(g)= 1.2, mu_(l) = 1.4`
`R_(1) = 0.2 m, R_(2) = - 0.2 m`
`f_(2) = + 70 cm`