Focal lengths of objective and eye-piece of microscope is 1.6 cm and 2.5 cm respectively. Distance between two lenses is 21.7 cm. If final image is formed at infinity, then magnification m = ......

Options

A. 11
B. 110
C. 1.1
D. 44

Answer

A, B

Explanation

`v_0=L-f_e=21.7-2.5=+19.2` cm

For objective `(1)/(v_0)-(1)/(u_0)=(1)/(f_0)`
`therefore (-1)/(u_0)=(1)/(f_0)-(1)/(v_0)`
`therefore (-1)/(u_0) =(19.2-1.6)/((1.6)(19.2))`
`therefore u_0=-1.745`cm
When image is formed at infinity magnification
`m=((v_0)/(u_0))((D)/(f_e))` where D=25 cm
`=((19.2)/(1.745))((25)/(2.5))`
`therefore m=110` cm