how the bending of light is related to focal length ?

Asked by nishant27_c | 20th Feb, 2010, 11:05: AM

Expert Answer:

Dear student,

If a magnifying glass is set at the end of a telescope when viewing stars?

To understand better, let us place a magnifying glass at one of two spots: at the entrance to the telescope or at the eyepiece of the telescope. If you put it at the entrance, it would bend the light before it had a chance to reach the main optic for the telescope. The effect would be to increase the light bending ability of the main optic and reduce the lens's focal length. This change would make it difficult to focus the telescope on distant objects, such as stars.

It would act as a close-up lens.That is what close-up lens attachments for cameras or even cheap reading glasses do: they help the camera lens or your eye form an image of very nearby objects. On the other hand, a magnifying glass held over the eyepiece of a telescope would increase the power of the telescope. You would have to adjust the focus of the telescope because the added magnifying glass will reduce the effective focal length of the eyepiece.

Hope you understand it better now.


Answered by  | 20th Feb, 2010, 12:15: PM

Queries asked on Sunday & after 7pm from Monday to Saturday will be answered after 12pm the next working day.