Optical Instruments & the Eye

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?

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

For large magnifying power of a telescope

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

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

In a microscope the objective is having focal length $f_o = 2\text{ cm}$ and eye-piece is having focal length $f_e = 4\text{ cm}$. The tube length is 32 cm. The magnification produced by this microscope for normal adjustment is ______.

A compound microscope is designed with two symmetric biconvex lenses. The objective lens is cut vertically, creating two identical plano-convex lenses. One of them is used in place of original objective lens. To retain same magnification keeping the object distance unchanged, the tube length has to be

The length of the compound microscope is 15 cm. The magnifying power for relaxed eye is 25. If the focal length of eye lens is 6 cm then the object distance for objective lens will be

A microscope has an objective of focal length 2 cm, eyepiece of focal length 4 cm and the tube length of 40 cm. If the distance of distinct vision of eye is 25 cm, the magnification in the microscope is

Simple microscope is used to see the object first in blue light and then a red light. Due to the change from blue to red light, its magnifying power

In compound microscope, the focal length and the aperture of the objective used is respectively

Focal length of objective of an astronomical telescope is 1.5 m. Under normal adjustment, length of telescope is 1.56 m. Focal length of the eyepiece is

A small telescope has an objective of focal length $140\text{ cm}$ and an eye piece of focal length $5.0\text{ cm}$. The magnifying power of telescope for viewing a distant object is:

An astronomical telescope has a large aperture to

A person is observing a bacteria through a compound microscope. For better analysis and to improve the resolving power he should

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

In a reflecting telescope, a secondary mirror is used to:

A person has been using spectacles of power $-1.0$ dioptre for distant vision and a separate reading glass of power $2.0$ dioptres. What is the least distance of distinct vision for this person:

An astronomical refracting telescope is being used by an observer to observe planets in normal adjustment. The focal lengths of the objective and eye piece used in the construction of the telescope are 20 m and 2 cm respectively. Consider the following statements about the telescope: (a) The distance between the objective and eye piece is 20.02 m

(a) The magnification of the telescope is ($-$) 1000

(b) The image of the planet is erect and diminished

(c) The aperture of eye piece is smaller than that of objective The correct statements are:

In normal adjustment, for a refracting telescope, the distance between objective and eye piece is $30\text{ cm}$. The focal length of the objective, when the angular magnification of the telescope is 2, will be:

A microscope was initially placed in air (refractive index 1). It is then immersed in oil (refractive index 2). For a light whose wavelength in air is $\lambda$, calculate the change of microscope's resolving power due to oil and choose the correct option.

Your friend is having eye sight problem. She is not able to see clearly a distant uniform window mesh and it appears to her as non-uniform and distorted. The doctor diagnosed the problem as:

The magnifying power of a refracting type of astronomical telescope is '$m$'. If focal length of eyepiece is doubled then the magnifying power will become

A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since:

Given below are two statements: one is labeled as Assertion A and the other is labeled as Reason R.

Assertion A: For a simple microscope, the angular size of the object equals the angular size of the image.

Reason R: Magnification is achieved as the small object can be kept much closer to the eye than 25 cm and hence it subtends a large angle.

In the light of the above statements, choose the most appropriate answer from the options given below:

An object viewed from a near point distance of 25 cm, using a microscopic lens with magnification '6', gives an unresolved image. A resolved image is observed at infinite distance with a total magnification double the earlier using an eyepiece along with the given lens and a tube of length 0.6 m, if the focal length of the eyepiece is equal to __________ cm.

An object is clearly seen through an astronomical telescope of length 50 cm. The focal lengths of its objective and eye-piece respectively, can be

The magnifying power of a telescope is high, if its objective and eyepiece have respectively

The magnifying power of a telescope with tube 60 cm is 5. What is the focal length of its eye piece?

By increasing the aperture of the objective lens, wavelength of light, focal length of the objective lens and the resolving power of an astronomical telescope respectively

If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5 mm, the focal length of the eye-piece, should be close to:

A compound microscope consists of an objective lens of focal length 1 cm and an eyepiece of focal length 5 cm with a separation of 10 cm.

The distance between an object and the objective lens, at which the strain on the eye is minimum is $\frac{n}{40}$ cm. The value of n is _____.

In a compound microscope, the magnified virtual image is formed at a distance of 25 cm from the eye-piece. The focal length of its objective lens is 1 cm. If the magnification is 100 and the tube length of the microscope is 20 cm, then the focal length of the eye-piece lens (in cm) is __________.

There are four convex lenses $L_1, L_2, L_3$ and $L_4$ of focal length $2, 4, 6$ and 8 cm, respectively. Two of these lenses from a telescope of length 10 cm and magnifying power 4. The objective and eye lenses are respectively

The magnifying power of a telescope is nine. When it is adjusted for parallel rays, the distance between the objective and eyepiece is 20 cm. The focal length of objective and eyepiece are respectively

A telescope has large diameter of the objective. Then its resolving power is

An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of

An observer looks at a distant tree of height $10\text{ m}$ with a telescope of magnifying power of $20$ To the observer the tree appears:

A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use, will be

A astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance

A telescope has an objective lens of focal length 150 cm and an eyepiece of focal length 5 cm. If a 50 m tall tower at a distance of 1 km is observed through this telescope in normal setting, the angle formed by the image of the tower is $\theta$, then $\theta$ is close to:

In an astronomical telescope in normal adjustment a straight black line of length L is drawn on inside part of objective lens. The eye-piece forms a real image of this line. The length of this image is $I$. The magnification of the telescope is

If the focal length of objective lens is increased then magnifying power of

In a compound microscope the focal length of objective lens is 1.2 cm and focal length of eye piece is 3.0 cm. When object is kept at 1.25 cm in front of objective, final image is formed at infinity. Magnifying power of the compound microscope should be:

The focal lengths of objective lens and eye lens of a Galilean Telescope are respectively 30 cm and 3.0 cm. Telescope produces virtual, erect image of an object situated far away from it at least distance of distinct vision from the eye lens. In this condition, the Magnifying Power of the Galilean Telescope should be:

This question has Statement-1 and Statement-2. Of the four choices given after the Statements, choose the one that best describes the two Statements.

Statement 1: Very large size telescopes are reflecting telescopes instead of refracting telescopes. Statement 2: It is easier to provide mechanical support to large size mirrors than large size lenses.

For a normal eye, the cornea of eye provides a converging power of 40 D and the least converging power of the eye lens behind the cornea is 20 D. Using this information, the distance between the retina and the cornea-eye lens can be estimated to be

The focal length of the objective and the eyepiece of a telescope are 50 cm and 5 cm respectively. If the telescope is focussed for distinct vision on a scale distant 2 m from its objective, then its magnifying power will be:

The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 cm. The focal length of lenses are

The image formed by an objective of a compound microscope is

An astronomical telescope has a large aperture to

Diameter of human eye lens is 2 mm. What will be the minimum distance between two points to resolve them, which are situated at a distance of 50 meter from eye. The wavelength of light is 5000 $\mathring{A}$

An astronomical telescope of tenfold angular magnification has a length of 44 cm. The focal length of the objective is

Exposure time of camera lens at $f/2.8$ setting is $\frac{1}{200}$ second. The correct time of exposure at $f/5.6$ is

Four lenses of focal length $\pm 15\text{ cm}$ and $\pm 150\text{ cm}$ are available for making a telescope. To produce the largest magnification, the focal length of the eyepiece should be