Physics - Geometrical Optics Question with Solution | TestHub

For the lens combination in contact:

$\frac{1}{f}=\frac{1}{f_1}+\frac{1}{f_2}=\frac{1}{10}+\frac{1}{(-20)}=\frac{1}{20}\Rightarrow f=+20\text{cm}$ (A) is correct

$u=-10\text{cm}:\frac{1}{v}=\frac{1}{f}+\frac{1}{u}=\frac{1}{20}-\frac{1}{10}=-\frac{1}{20}\Rightarrow v=-20\text{cm}$

$m=\frac{v}{u}=\frac{-20}{-10}=+2\Rightarrow h_I=2\times 1=2\text{cm}$ (B) is correct

Magnification is +2 (not -2), and v < 0 means the image is virtual, so (C) and (D) are wrong.

Hence (A) and (B).