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The Magnifying Power of a Converging Lens Used as a Simple Microscope is - Physics

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प्रश्न

The magnifying power of a converging lens used as a simple microscope is `(1+D/f).` A compound microscope is a combination of two such converging lenses. Why don't we have magnifying power `(1+D/f_0)(1+D/f_0)`?In other words, why can the objective not be treated as a simple microscope but the eyepiece can?

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उत्तर

In a simple microscope, the converging lens is used to magnify the object. It is done by the eyepiece in a compound microscope. But the purpose of the objective lens is the same, i.e., to form an enlarged, real and inverted image of the object at a distance less than the focal length of the eyepiece. So, its magnification power cannot be expressed in a way it is expressed for a simple microscope.

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पाठ 19: Optical Instruments - Short Answers [पृष्ठ ४३०]

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एचसी वर्मा Concepts of Physics Vol. 1 [English] Class 11 and 12
पाठ 19 Optical Instruments
Short Answers | Q 7 | पृष्ठ ४३०

संबंधित प्रश्‍न

A giant refracting telescope has an objective lens of focal length 15 m. If an eye piece of focal length 1.0 cm is used, what is the angular magnification of the telescope ?


Draw a labelled ray diagram showing the formation of a final image by a compound microscope at least distance of distinct vision


The total magnification produced by a compound microscope is 20. The magnification produced by the eye piece is 5. The microscope is focussed on a certain object. The distance between the objective and eyepiece is observed to be 14 cm. If least distance of distinct vision is 20 cm, calculate the focal length of the objective and the eye piece.


A person with a normal near point (25 cm) using a compound microscope with the objective of focal length 8.0 mm and an eyepiece of focal length 2.5 cm can bring an object placed at 9.0 mm from the objective in sharp focus. What is the separation between the two lenses? Calculate the magnifying power of the microscope.


Magnifying power of a simple microscope is inversely proportional to the focal length of the lens. What then stops us from using a convex lens of smaller and smaller focal length and achieving greater and greater magnifying power?


Why must both the objective and the eyepiece of a compound microscope have short focal lengths?


When viewing through a compound microscope, our eyes should be positioned not on the eyepiece but a short distance away from it for best viewing. Why? How much should be that short distance between the eye and eyepiece?


Does the magnifying power of a microscope depend on the colour of the light used? Justify your answer.


Draw a ray diagram showing image formation in a compound microscope ?


How is 'limit of resolution' related to resolving power of a microscope ?


Suggest two ways by which the resolving power of a microscope can be increased?


Draw a ray diagram to show the working of a compound microscope. Deduce an expression for the total magnification when the final image is formed at the near point.

In a compound microscope, an object is placed at a distance of 1.5 cm from the objective of focal length 1.25 cm. If the eye piece has a focal length of 5 cm and the final image is formed at the near point, estimate the magnifying power of the microscope.


Draw the labelled ray diagram for the formation of image by a compound microscope.

Derive the expression for the total magnification of a compound microscope. Explain why both the objective and the eyepiece of a compound microscope must have short focal lengths.


A man is looking at a small object placed at his near point. Without altering the position of his eye or the object, he puts a simple microscope of magnifying power 5 X before his eyes. The angular magnification achieved is


In which of the following the final image is erect?
(a) Simple microscope
(b) Compound microscope
(c) Astronomical telescope
(d) Galilean telescope


A simple microscope is rated 5 X for a normal relaxed eye. What will be its magnifying power for a relaxed farsighted eye whose near point is 40 cm?


Draw a labelled ray diagram showing the formation of image by a compound microscope in normal adjustment. Derive the expression for its magnifying power.


How does the resolving power of a microscope change when
(i) the diameter of the objective lens is decreased?
(ii) the wavelength of the incident light is increased ?
Justify your answer in each case.


In the case of a regular prism, in minimum deviation position, the angle made by the refracted ray (inside the prism) with the normal drawn to the refracting surface is ______.


A compound microscope consists of two converging lenses. One of them, of smaller aperture and smaller focal length, is called objective and the other of slightly larger aperture and slightly larger focal length is called eye-piece. Both lenses are fitted in a tube with an arrangement to vary the distance between them. A tiny object is placed in front of the objective at a distance slightly greater than its focal length. The objective produces the image of the object which acts as an object for the eye-piece. The eye-piece, in turn, produces the final magnified image.

The magnification due to a compound microscope does not depend upon ______.


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