Opera glass have a minimum length of 20 cm and a magnifying power of 5 when viewing distant objects. The focal lengths of lenses used are

25 c m, 5 c m

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25 c m, - 5 c m

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2 c m, 2 c m

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15 c m, 10 c m

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Solution

The correct option is A $25 c m, 5 c m$
The formula for the length of the tube is: $L = f_{o} - f_{e}$
Also, the magnification is given by: $m = \frac{f_{o}}{f_{e}}$
Substituting the values for $m$ and $L$ , the values of the respective focal lengths are $25$ and $5$ cms.

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Opera glass have a minimum length of 20 cm and a magnifying power of 5 when viewing distant objects. The focal lengths of lenses used are

The correct option is A 25cm,5cmThe formula for the length of the tube is: L=fo−feAlso, the magnification is given by: m=fofeSubstituting the values for m and L, the values of the respective focal lengths are 25 and 5 cms.

The correct option is A $25 c m, 5 c m$
The formula for the length of the tube is: $L = f_{o} - f_{e}$
Also, the magnification is given by: $m = \frac{f_{o}}{f_{e}}$
Substituting the values for $m$ and $L$ , the values of the respective focal lengths are $25$ and $5$ cms.