An object is viewed using a simple microscope of focal length 12 cm . To obtain the maximum angular magnification, at what distance from the lens should the object be positioned? The least distance for clear vision is

Question

Quantrex Academy · Accepted Answer

Correct answer: B. 8.1 cm

For maximum angular magnification, the final image must be formed at the least distance of distinct vision.

Given:
Focal length,

f = +12 \text{ cm}

Image distance,

v = -D = -25 \text{ cm}

Using the lens formula:

\dfrac{1}{v} - \dfrac{1}{u} = \dfrac{1}{f}

\dfrac{1}{u} = \dfrac{1}{v} - \dfrac{1}{f}

\dfrac{1}{u} = \dfrac{1}{-25} - \dfrac{1}{12}

\dfrac{1}{u} = \dfrac{-12 - 25}{300} = -\dfrac{37}{300}

u = -\dfrac{300}{37} \text{ cm} \approx -8.1 \text{ cm}

The object should be positioned at a distance of

8.1 \text{ cm}

from the lens.

An object is viewed using a simple microscope of focal length 12 cm...

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