Q11. A compound microscope has an objective of focal length 1 cm and eyepiece of focal length 5 cm. Lens separation is 20 cm. With final image at infinity, the magnitude of total angular magnification (D = 25 cm) is:
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Question

Q11. A compound microscope has an objective of focal length 1 cm and eyepiece of focal length 5 cm. Lens separation is 20 cm. With final image at infinity, the magnitude of total angular magnification (D = 25 cm) is:

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G1 Physics · Accepted Answer

GIVEN: Objective focal length fₒ = 1 cm; eyepiece fₑ = 5 cm; lens separation L = 20 cm; D = 25 cm; final image at ∞. Step 1: For a final image at infinity, the objective's real intermediate image lies at the eyepiece front focus, 5 cm in front of the eyepiece. Step 2: Therefore objective image distance vₒ = L − fₑ = 20 − 5 = 15 cm. Step 3: Exact objective linear magnification magnitude |mₒ| = (vₒ/fₒ) − 1 = (15/1) − 1 = 14. [This follows from the objective lens formula.] Step 4: Eyepiece angular…