Q34. A microscope has an eyepiece focal length 6 cm. Its final image is initially at infinity. Without disturbing the object or objective, the eyepiece is shifted to form a final image at the near point D = 30 cm. Displacement is:
Options

Question

Q34. A microscope has an eyepiece focal length 6 cm. Its final image is initially at infinity. Without disturbing the object or objective, the eyepiece is shifted to form a final image at the near point D = 30 cm. Displacement is:

Options

G1 Physics · Accepted Answer

GIVEN: Eyepiece focal length fₑ = 6 cm; observer's near point D = 30 cm; intermediate image remains fixed. Step 1: Initially, image at infinity requires eyepiece object distance s₁ = fₑ = 6 cm. Step 2: To form a virtual image at −30 cm, use 1/6 = −1/30 + 1/s₂. Step 3: 1/s₂ = 1/6 + 1/30 = 6/30 = 1/5 ⇒ s₂ = 5 cm. Step 4: Eyepiece must move closer to the fixed intermediate image by Δ = s₁ − s₂ = 6 − 5 = 1 cm. FINAL ANSWER: 1 cm towards objective. Option B.