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प्रश्न
Focal length : metre : : power of lens : _______
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उत्तर
Focal length : metre : : power of lens : dioptre
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संबंधित प्रश्न
Calculate the focal length of a corrective lens having power +2.5 D.
What is meant by a power of a lens? Define its SI unit.
What does sign of power (+ve or –ve) indicate?
Define 1 dioptre of power of a lens.
Find the power of a concave lens of focal length 2m.
(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.
A student uses a lens of focal length 40 cm and another of –20 cm. Write the nature and power of each lens
What can you see in a completely dark room? If you switch on an electric bulb in this dark room as a light source, explain how you could now see:
(a) the electric bulb
(b) a piece of white paper
How is the power of a lens related to its focal length?
The power of a lens is, −2 D. What is its focal length?
What is the nature of a lens having a power of + 0.5 D?
What is the nature of a lens whose power is, −4 D?
Fill in the following blank with suitable word:
For converging lenses, the power is __________ while for diverging lenses, the power is ___________.
A convex lens of power 5 D and a concave lens of power 7.5 D are placed in contact with each other. What is the :
(a) power of this combination of lenses?
(b) focal length of this combination of lenses?
Two lenses A and B have focal lengths of +20 cm and, −10 cm, respectively.
(a) What is the nature of lens A and lens B?
(b) What is the power of lens A and lens B?
(c) What is the power of combination if lenses A and B are held close together?
A converging lens has a focal length of 50 cm. The power of this lens is:
Define the term focal length of a lens.
How is the power of a lens related to its focal length?
The power of a lens is + 1.0 D is :
How does focal length of a lens change when red light incident on it is replaced by violet light? Give reason for your answer.
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 two surfaces of equal radii R and refractive index \[m = 1 \cdot 5\]
A symmetric double convex lens in cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power a cut-lens will be
A symmetric double convex lens is cut in two equal parts by a plane containing the principal axis. If the power of the original lens was 4 D, the power of a divided lens will be
A screen is placed a distance 40 cm away from an illuminated object. A converging lens is placed between the source and the screen and its is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens
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 pin of length 2.00 cm is placed perpendicular to the principal axis of a converging lens. An inverted image of size 1.00 cm is formed at a distance of 40.0 cm from the pin. Find the focal length of the lens and its distance from the pin.
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?
The power of a lens is +2.0 D. Find its focal length and state the kind of 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.
If there is a convex lens of focal length 75 cm and a concave lens of focal length 40 cm, then calculate their combined power and combined focal length.
Power of a lens is – 4D, then its focal length is
According to Rayleigh’s scattering law, the amount of scattering of light is inversely proportional to the fourth power of its ______.
A point object is placed at O in front of a glass sphere as shown in figure.
Show the formation of the image by the sphere.
The same size images are formed by a convex lens when the object is placed at 20 cm or at 10 cm from the lens. The focal length of convex lens is ______ cm.
The lens of power + 1·0 D is ______.
