A compound microscope has an objective lens of focal length fo = 1.0 cm and an eyepiece of focal length fe = 2.5 cm. If an object is placed at a distance uo = 1.1 cm from the objective lens, what is the magnifying power of the microscope when the final image is formed at the near point of distinct vision (D = 25 cm)?
Answer and explanation
Correct answer: A. 110
Given and :
.
.
.
.
- Step 1: The total magnifying power of a compound microscope when the final image is formed at the near point is: .
- Step 2: Calculate image distance for the objective lens using lens formula :
- Step 3: Objective linear magnification is: .
- Step 4: Eyepiece angular magnification at near point (, ) is:
- Step 5: Total magnifying power is: .
Answer
110
Why not the others: '100' uses normal adjustment formula instead of near point adjustment ; '55' divides by 2; '250' multiplies by 25.
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