A microscope has an objective of focal length 2 cm, an eyepiece of focal length 4 cm and a tube length of 40 cm. If the distance…

Question

A microscope has an objective of focal length 2 cm, an eyepiece of focal length 4 cm and a tube length of 40 cm. If the distance of distinct vision of the eye is 25 cm, the magnification of the microscope is:

1. A. 100
2. B. 125 (Correct answer)
3. C. 150
4. D. 250

Correct Answer

Option B — 125

Detailed Solution & Explanation

The correct answer is 125.

Key Points

• Magnification of a compound microscope: $m=\dfrac{L}{f_o}\times\dfrac{D}{f_e}$.
• Given $L=40$ cm, $f_o=2$ cm, $f_e=4$ cm, $D=25$ cm.
• $m=\dfrac{40}{2}\times\dfrac{25}{4}=20\times 6.25=125$.