Question

The focal length of objective and eye lens of a microscope are $4cm$ and $8cm$ respectively. If the least distance of distinct vision is $24cm$ and object distance is $4.5cm$ from the objective lens, then the magnifying power of the microscope will be

• A. 18
• B. 32
• C. 64
• D. 20

Answer 1

Answer: (B)

For objective lens $\frac{1}{f_o}=\frac{1}{v_o}-\frac{1}{u_o}$
$\Rightarrow \frac{1}{(+4)}+\frac{1}{v_o}-\frac{1}{(-4.5)}$
$\Rightarrow v_o=36cm$
$\therefore \left|m_D\right|=\frac{v_o}{u_o}\left(1+\frac{D}{f_e}\right)$
$=\frac{36}{4.5}\left(1+\frac{24}{8}\right)=32$