Wave Optics

Question

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A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. What is the magnifying power of the telescope for viewing distant objects when the final image is formed at the least distance of distinct vision (25 cm)?

Solution

Given,
Focal length of objective lens, f₀ = 140 cm
Focal length of eyepiece, f_e = 5 cm

Magnifying power when the final image is formed at least distance of distinct vision, m

= - \frac{f_{0}}{f_{e}} (1 + \frac{f_{e}}{D})

m =

- \frac{140}{5} (1 + \frac{5}{25}) - 33.6 .

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Wave Optics

A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. What is the magnifying power of the telescope for viewing distant objects when the final image is formed at the least distance of distinct vision (25 cm)?

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