Question

A compound microscope has a magnifying power of 100 when the image is formed at infinity. The objective has a focal length of 0.5 cm and the tube length is 6.5 cm, then the focal length of the eye-piece is –

• A. 0.2 cm
• B. 2.5 cm
• C. 2 cm
• D. 4.0 cm

Answer 1

Answer: (C)

2 cm

Answer 2

L_ฅ = v_o + f_e = 6.5 cm, f_o = 0.5 cm

v_o = (6.5 –f_e)





…..(1)

 2f_e = 6 – f_e

$\mathrm { f } _ { \mathrm { e } } = 2 \mathrm {~cm}$