Optical Instruments
Optical Instruments: Overview
This topic covers concepts, such as Optical Instruments, Eye as Optical Instrument, Defects of Eye, Microscopes, Simple Microscope, Linear Magnification in Optical Instrument, Angular Magnification in Optical Instrument, Compound Microscope, etc.
Important Questions on Optical Instruments
An astronomical telescope uses two lenses of powers 10 D and 1 D.Its magnifying power in normal adjustment would be:

The expression for magnifying power of compound microscope is

The expression for astronomical telescope magnifying power is

What is astigmatism? How is it corrected?

In a compound microscope, the intermediate image is

The focal lengths of the objective and the eye piece of a compound microscope are and respectively. The distance between the objective and the eye piece is The final image formed by the eye piece is at infinity. The two lenses are thin. The distance in of the object and the image produced by the objective, measured from the objective lens, are respectively

We can see that in normal eye the things taking part in refraction are the cornea, aqueous humour, crystalline eye lens and the vitreous humour. Let us assume that we consider only things namely the cornea and the eye lens. The power of the cornea is fixed and equal to . The ciliary muscles can change the power of the eye lens which varies between to . Calculate the least distance of distinct vision for such an eye.

Which of the following is correct regarding microscope and telescope?

In an astronomical telescope, and , then find out the maximum magnification of a distant object. Take least distance of clear vision, .

What is the nature of the intermediate image in a compound microscope?

Cassegrain Telescope is a type of

Total magnification of compound microscope is while magnification for eye piece is . If final image is formed at near point which is taken then focal length of eye piece is

The focal length of magnifying glass is then magnifying power this instrument when image is formed at infinity is ( near point for normal eye)

An object is at distance from compound microscope of focal length and for objective and eye piece respectively. Magnifying power of microscope when image is formed at near point is

The focal length of an objective of a telescope is 3 meter and diameter 15 cm. Assuming for a normal eye, the diameter of the pupil is 3 mm for its complete use, the focal length of eye piece must be

An astronomical telescope has a converging eyepiece of focal length and an objective of focal length . When the final image is formed at the least distance of distinct vision, the separation between the two lenses is

An observer looks at a tree of height with a telescope of magnifying power . To him the tree appears

A presbyopic patient can see objects only when they lie between and from the eye. Then the focal length of the correcting lens required while reading is

An observer looks at a distant tree of height with a telescope of the magnifying power of . To the observer, the tree appears as

An object is placed at a distance from a simple microscope of focal length . The angular magnification obtained depends
