# An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20.  To the observer the tree appears Option 1) 10 times taller.   Option 2) 10 times nearer.   Option 3)  20 times taller.   Option 4) 20 times nearer.

P Plabita

As we learnt in

Length of Astronomical Telescope -

$L=f_{o}+\frac{f_{e}\, D}{f_{e}+ D}$

- wherein

$f_{o}=$ Focal length of objective.

$f_{e}=$ Focal length of eyepiece

Telescope resolves and brings the object closer which is far away from the telescope. Hence for telescope with magnifying power 20, the free appears 20 times nearer.

Correct option is 4.

Option 1)

10 times taller.

This is an incorrect option.

Option 2)

10 times nearer.

This is an incorrect option.

Option 3)

20 times taller.

This is an incorrect option.

Option 4)

20 times nearer.

This is the correct option.

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