Question

The focal lengths of the objective and the eye-piece of a compound microscope are 2.0 cm and 3.0 cm respectively. The distance between the objective and the eye-piece is 15.0 cm. The final image formed by the eye-piece is at infinity. The two lenses are thin. The distances in cm of the object and the image produced by the objective measured from the objective lens are respectively

• A. 2.4 and 12.0
• B. 2.4 and 15.0
• C. 2.3 and 12.0
• D. 2.3 and 3.0

Answer 1

The correct option is A 2.4 and 12.0

Given that $f_0=2cm,f_e=3cm,L_{\infty }=15cm$
By using $L_{\infty }+f_e\Rightarrow 15=v_0+3\Rightarrow v_0=12cm.Also\frac{v_0}{u_0}=\frac{v_0-f_0}{f_0}\Rightarrow \frac{12}{u_0}=\frac{12-2}{2}\Rightarrow u_0=2.4cm$.