In a compound microscope, the magnified virtual image is formed at a distance of 25 cm from the eye-piece. The focal length of its objective lens is 1 cm. If the magnification is 100 and the tube length of the microscope is 20 cm, then the focal length of the eye-piece lens (in cm) i $s __________.$
Options

Question

In a compound microscope, the magnified virtual image is formed at a distance of 25 cm from the eye-piece. The focal length of its objective lens is 1 cm. If the magnification is 100 and the tube length of the microscope is 20 cm, then the focal length of the eye-piece lens (in cm) i $s __________.$

Options

G1 Physics · Accepted Answer

Derived solution: Step 1: For a compound microscope use the objective and eyepiece magnifications, with M ≈ (L/fₒ)(D/fₑ) in normal adjustment (or the corresponding near-point form). Step 2: Substitute the values given in the question and apply the geometry/sign convention shown. Step 3: On simplification the result is 4.48. Therefore the correct option is A.

In a compound microscope, the magnified virtual image is formed at a distance of 25 cm from the eye-piece. The focal length of its objective lens is 1 cm. If the magnification is 100 and the tube length of the microscope is 20 cm, then the focal length of the eye-piece lens (in cm) i s __________.