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प्रश्न
Draw a ray diagram showing the image formation by a compound microscope. Hence obtained expression for total magnification when the image is formed at infinity.
उत्तर
A compound microscope consists of two convex lenses co-axially separated by some distance. The lens nearer to the object is called the objective. The lens through which the final image is viewed is called the eyepiece.
Magnifying power, when final image is at infinity:
The magnification produced by the compound microscope is the product of the magnifications produced by the eyepiece and objective.
`∴M = M_e xx M_0 ...... (1)`
Where, Me and M0 are the magnifying powers of the eyepiece and objective respectively.
If u0 is the distance of the object from the objective and v0 is the distance of the image from the objective, then the magnifying power of the
objective is `M_0 = (h')/h =L/f_0 ( using tanβ = (h/f_0) = =(h/L))`
Where, h, h' are object and image heights respectively and f0 is the focal length of the objective.
L is the tube length i.e. the distance between the second focal point of the objective and the first focal point of the eyepiece.
When the final image is at infinity, `M_e = D/f_e`
Magnifying power of compound microscope,`M = M_0 xx M_e = L/f_0 xx D/f_e`
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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.
You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct a compound microscope?
| Lenses | Power (D) | Aperture (cm) |
| L1 | 3 | 8 |
| L2 | 6 | 1 |
| L3 | 10 | 1 |
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.
Distinguish between myopia and hypermetropia. Show diagrammatically how these defects can be corrected.
Can the image formed by a simple microscope be projected on a screen without using any additional lens or mirror?
What is the advantage of a compound microscope over a simple microscope?
On increasing the focal length of the objective, the magnifying power ______.
| 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.
What is meant by a microscope in normal use?
