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An Object is Placed at a Distance U from a Simple Microscope of Focal Length F. - Physics

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प्रश्न

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

पर्याय

  • on f but not on u

  • on u but not on f

  • on f as well as u

  • neither on f nor on u

MCQ
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उत्तर

 on f as well as u

​The angular magnification is the ratio of the angle subtended by the image to the angle subtended by the object on an unaided eye.
In a simple microscope,

m=`(h/u)/(h/D)`

Here,

u = Object distance from the lens

D = Image distance from the lens

h = Height of the object

In normal adjustment, the object is placed at a distamce equal to  ​focal length(f)  from the lens and then magnification is given by m = D/f.
For u < f, m = D/f +1.

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पाठ 19: Optical Instruments - MCQ [पृष्ठ ४३१]

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एचसी वर्मा Concepts of Physics Vol. 1 [English] Class 11 and 12
पाठ 19 Optical Instruments
MCQ | Q 9 | पृष्ठ ४३१

संबंधित प्रश्‍न

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 compound microscope consists of an objective lens of focal length 2.0 cm and an eyepiece of focal length 6.25 cm separated by a distance of 15 cm. How far from the objective should an object be placed in order to obtain the final image at

  1. the least distance of distinct vision (25 cm), and
  2. infinity?

What is the magnifying power of the microscope in each case?


Define the magnifying power of a compound microscope when the final image is formed at infinity. Why must both the objective and the eyepiece of a compound microscope has short focal lengths? Explain.


How can the resolving power of a compound microscope be increased? Use relevant formula to support your answer.


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 ?


A compound microscope has an objective of focal length 1.25 cm and eyepiece of focal length 5 cm. A small object is kept at 2.5 cm from the objective. If the final image formed is at infinity, find the distance between the objective and the eyepiece ?


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?


Consider the following two statements :-

(A) Line spectra contain information about atoms.

(B) Band spectra contain information about molecules.


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?


An eye can distinguish between two points of an object if they are separated by more than 0.22 mm when the object is placed at 25 cm from the eye. The object is now seen by a compound microscope having a 20 D objective and 10 D eyepiece separated by a distance of 20 cm. The final image is formed at 25 cm from the eye. What is the minimum separation between two points of the object which can now be distinguished?


A lady uses + 1.5 D glasses to have normal vision from 25 cm onwards. She uses a 20 D lens as a simple microscope to see an object. Find the maximum magnifying power if she uses the microscope (a) together with her glass (b) without the glass. Do the answers suggest that an object can be more clearly seen through a microscope  without using the correcting glasses?


Define the magnifying power of a microscope in terms of visual angle.


A convex lens of a focal length 5 cm is used as a simple microscope. Where should an object be placed so that the image formed by it lies at the least distance of distinct vision (D = 25 cm)?


A microscope is focussed on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again?


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.

In a compound microscope, the images formed by the objective and the eye-piece are respectively.


The focal lengths of the objective and the eye-piece of a compound microscope are 1.0 cm and 2.5 cm respectively. Find the tube length of the microscope for obtaining a magnification of 300.


What is meant by a microscope in normal use?


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