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What is the near point focusing? - Physics

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प्रश्न

What is the near point focusing?

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उत्तर

The image is formed at a near point, i.e. 25 cm for the normal eye. This distance is also called as least distance D of distinct vision. In this position, the eye feels comfortable but there is little strain on the eye.

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Optical Instruments
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पाठ 7: Wave Optics - Evaluation [पृष्ठ १०४]

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सामाचीर कलवी Physics - Volume 1 and 2 [English] Class 12 TN Board
पाठ 7 Wave Optics
Evaluation | Q 39. | पृष्ठ १०४

संबंधित प्रश्‍न

Answer the following question in detail.

Define and describe the magnifying power of an optical instrument.


Answer the following question in detail.

How does magnifying power differ from linear or lateral magnification?


Answer the following question in detail.

Obtain the expressions for magnifying power and the length of an astronomical telescope under normal adjustments.


Answer the following question in detail.

What is the limitation in increasing the magnifying powers of a simple microscope?


Discuss about simple microscope and obtain the equations for magnification for near point focusing and normal focusing.


What are the advantages and disadvantages of using a reflecting telescope?


What is the use of an erecting lens in a terrestrial telescope?


What is the use of collimator in a spectrmeter?


What are the uses of spectrometer?


What is astigmatism? What is its remedy?


Mention different parts of the spectrometer.


A compound microscope has a magnification of 30. The focal length of eye piece is 5 cm. Assuming the final image to be at least distance of distinct vision, find the magnification produced by the objective.


The near point and the far point for a person are 50 cm and 500 cm, respectively. Calculate the power of the lens the person should wear to read a book held in hand at 25 cm. What maximum distance is clearly visible for the person with this lens on the eye?


When a convex lens of 12.5 cm focal length is used as a magnifying glass, normal eye can see an object clearly at a distance of 25 cm. The magnifying power of the instrument is ____________.


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.


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


The speed of light in media 'A' and 'B' are 2.0 × 1010 cm/s and 1.5 × 1010 cm/s respectively. A ray of light enters from medium B to A at an incident angle 'θ'. If the ray suffers total internal reflection, then ______.


In the adjoining figure, AB represents the incident ray, and BK is the reflected ray. If angle BCF = θ, then ∠BFP is given by ______.

 


A camera objective has an aperture diameter of d. If the aperture is reduced to diameter d/2, the exposure time under identical conditions of light should be made ______.


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