Question

एक आदमी केवल 3 मीटर तक देख सकता
है। उसके लिए 12 मीटर तक स्पष्ट देखने के
लिए निर्धारित लेंस की फोकस दूरी है।
i) - 3 मीटर + 4 मीटर
iii) – 4 मीटर iv) + 12 मीटर। 1​

Answer 1

Answer:

Focal length of the lens required for the eye is f = - 4cm

Explanation:

As we know that man can see clearly till d = 3 m

Now he would like to see the distance till d = 12 m

so here we can use lens formula where object distance is d = 12 m and its image must form at d = 3 m

so we have

$\frac{1}{d_i} - \frac{1}{d_o} = \frac{1}{f}$

$\frac{1}{-3} + \frac{1}{12} = \frac{1}{f}$

$f = -4 cm$

So focal length of the lens required is f = - 4cm

#Learn

Topic : Lens

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