Q20. A compound microscope has fₒ = 1 cm, fₑ = 5 cm. Tube length is increased from 20 cm to 21 cm and the object is readjusted so the final image remains at infinity. The total angular magnification magnitude:
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Q20. A compound microscope has fₒ = 1 cm, fₑ = 5 cm. Tube length is increased from 20 cm to 21 cm and the object is readjusted so the final image remains at infinity. The total angular magnification magnitude:

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G1 Physics · Accepted Answer

GIVEN: fₒ = 1 cm, fₑ = 5 cm, D = 25 cm; telescope-like tube length NOT used: this is a compound microscope. Step 1: For final image at infinity, vₒ = L − fₑ and |mₒ| = vₒ/fₒ − 1. Step 2: Initially L₁ = 20 cm ⇒ vₒ₁ = 20 − 5 = 15 cm ⇒ |mₒ₁| = 15/1 − 1 = 14. Step 3: Eyepiece magnification mₑ = 25/5 = 5; thus |M₁| = 14 × 5 = 70. Step 4: After readjustment L₂ = 21 cm ⇒ vₒ₂ = 21 − 5 = 16 cm ⇒ |mₒ₂| = 16/1 − 1 = 15. Step 5: |M₂| = 15 × 5 = 75; increase = 75 − 70 = 5. FINAL ANSWER: Increases by 5. Opti…