Correct Answer - A::C::D

`(omega_1)/(f_1)+(omega_2)/(f_2)=0`

`:. |omega_1/omega_2|=|(f_1)/(f_2)|`

Let 1-stands for flint glass and 2-stands for crown

glass. Then,

`|(f_1)/(f_2)|=3/2 or |f_1|=1.5|f_2|`

Focal length of flint glass is more. So, its power is

less. Combined focal length (and hence combined power)

is positive. So, convex lens (converging

lens) should be made up of crown glass (having

more positive power).

Now, `1/F=1/(f_1)+1/(f_2)`

`:. 1/150=1/(-1.5f)+1/f`

Solving this equation, we get

`f_2=f=50 cm` and

`f_1=-1.5,f=-75 cm`