List of top Physics Questions on Optical Instruments

Keeping the length of an astronomical telescope constant in normal adjustment, to increase its magnification from 4 to 9, the focal length of the eyepiece is to be decreased by 10 cm. The length of the telescope is

To improve the resolving power of a compound microscope we should

In an optical instrument- microscope, the wavelength of light used are \(λ_1 = 6800\) Å and \(λ_2 = 5100\) Å. The ratio of the resolving power of microscope corresponding to '\(λ_1\)' to that for '\(λ_2\)' is

A simple microscope is a combination of two lenses in contact. Their powers are \(+20\text{D}\) and \(-4\text{D}\). The distance of distinct vision is \(25 \text{cm}\). When seen through the microscope, the size of the image of an object \(3 \text{mm}\) high is

In telescopes for a given wavelength, the objectives with large aperture are used for

A simple microscope is used to see the object first in blue light and then in red light. Due to the change from blue to red light, what is the effect on its magnifying power?

For large magnifying power of a telescope

In a microscope of tube length $10\,\text{cm}$ two convex lenses are arranged with focal lengths $2\,\text{cm}$ and $5\,\text{cm}$. Total magnification obtained with this system for normal adjustment is $(5)^k$. The value of $k$ is ___.

A telescope has an objective lens of focal length 144 cm and an eyepiece of focal length 6·0 cm. The magnifying power and the length of telescope tube will be respectively :

In a telescope the objective has much larger aperture than the eyepiece. Why?

Write two advantages of reflecting telescope over refracting telescope.

Draw a labelled ray diagram of a refracting telescope when it forms image of a distant object at infinity. Derive the expression for its magnifying power.

Give two reasons to explain why a reflecting telescope is preferred over a refracting telescope.

Draw the ray diagram to show the image formation by a refracting telescope and write the expression for angular magnification for the telescope in normal adjustment.

In a telescope the objective has much larger aperture than the eyepiece. Why?

Write two advantages of reflecting telescope over refracting telescope.

Draw a labelled ray diagram of a refracting telescope when it forms image of a distant object at infinity. Derive the expression for its magnifying power.

Draw the ray diagram to show the image formation by a refracting telescope and write the expression for angular magnification for the telescope in normal adjustment.

Give two reasons to explain why a reflecting telescope is preferred over a refracting telescope.

Two convex lenses of different focal lengths are in contact with each other. If the focal length of each lens is doubled, the focal power of the combination

An astronomical telescope in normal adjustment has magnifying power \(5\) for distant objects. The separation between the objective and the eyepiece is \(36\) cm. The focal lengths of the objective and the eyepiece are respectively

In an astronomical telescope of $135\text{ cm}$ length kept in normal adjustment, if the difference between the focal lengths of the objective and eyepiece is $125\text{ cm}$, then the magnification of the telescope is:

The distance between the objective and eyepiece of an astronomical telescope in normal adjustment is $27\text{ cm}$ and its magnifying power is $8$. What is the focal length of the eyepiece?

The unit of power of a lens is

The magnifying power of a simple microscope can be increased by using