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प्रश्न
Give the usual name for the following:
A point inside a lens through which the light passes undeviated.
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उत्तर
The usual name for a point inside a lens through which light passes undeviated is the optical center
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संबंधित प्रश्न
What does sign of power (+ve or –ve) indicate?
State the power of a lens S.I. unit.
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
(a) At what distance should the lens be held from the figure in order to view the squares distinctly with the maximum possible magnifying power?
(b) What is the magnification in this case?
(c) Is the magnification equal to the magnifying power in this case? Explain.
You have two lenses A and B of focal lengths +10 cm and –10 cm, respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed 8 cm from the lens? Draw a ray diagram to justify your answer
A student uses a lens of focal length 40 cm and another of –20 cm. Write the nature and power of each lens
A converging lens has focal length of 50 mm. What is the power of the lens?
An object of height 4 cm is placed at a distance of 15 cm in front of a concave lens of power, −10 dioptres. Find the size of the image.
How does the power of a lens change if its focal length is doubled?
Define power of a lens. Write its units. Deduce the relation `1/f =1/f_1 +1/f_2`for two thin lenses kept in contact coaxially.
A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is double of the other. Find the radii, if the refractive index of the material of the lens is 1.5.
A convex lens produces a double size real image when an object is placed at a distance of 18 cm from it. Where should the object be placed to produce a triple size real image?
A diverging lens of focal length 20 cm and a converging lens of focal length 30 cm are placed 15 cm apart with their principal axes coinciding. Where should an object be placed on the principal axis so that its image is formed at infinity?
How is accommodation produced?
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
The following diagram shows the object O and the image I formed by a lens. Copy the diagram and on it mark the positions of the lens LL’ and focus (F). Name the lens.
Complete the diagram to show the formation of the image of the object AB.
(i) Name the Lens LL’.
(ii) Where is the image of the object AB formed?
(iii) State three characteristics of the image.
The focal length of a double convex lens is equal to the radius of curvature of either surface. What is the refractive index of its material?
A positive power of a lens indicates a:
For a lens with \[f = +12\,cm\], \[R_1 = +10\,cm\] and \[R_2 = -15\,cm\], the lens maker's formula \[\frac{1}{f}=(n-1)\left(\frac{1}{R_1}-\frac{1}{R_2}\right)\] gives the refractive index of the glass as:
