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प्रश्न
Focal length : metre : : power of lens : _______
उत्तर
Focal length : metre : : power of lens : dioptre
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संबंधित प्रश्न
Calculate the focal length of a corrective lens having power +2D.
Calculate the focal length of a corrective lens having power +2.5 D.
How unit of power related to focal length of a lens?
Find the focal length of a lens of power −2.0 D. What type of lens is this?
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
The lens mentioned in 6(b) above is of focal length 25cm. Calculate the power of the 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
Give the usual name for the following:
A point inside a lens through which the light passes undeviated.
Which of the two has a greater power: a lens of short focal length or a lens of large focal length?
Which has more power : a thick convex lens or a thin convex lens, made of the same glass? Give reason for your choice.
A converging lens has focal length of 50 mm. What is the power of the lens?
What is the power of a convex lens lens whose focal length is 80 cm?
A diverging lens has focal length of 3 cm. Calculate the power.
The optician's prescription for a spectacle lens is marked +0.5 D. What is the:
(a) nature of spectacle lens?
(b) focal length of spectacle lens?
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 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 combination of lenses for a camera contains two converging lenses of focal lengths 20 cm and 40 cm and a diverging lens of focal length 50 cm. Find the power and focal length of the combination.A optical instrument in which the above arrangement of convex lens is used is a convex lens used to burn paper by focusing sunlight.
A converging lens has a focal length of 50 cm. The power of this lens is:
The power of a lens is +2.0D. Its focal length should be :
Define the term focal length of a lens.
The power of a lens is + 1.0 D is :
Express the power (with sign) of a concave lens of focal length 20 cm.
Find the radius of curvature of the convex surface of a plano-convex lens, whose focal length is 0.3 m and the refractive index of the material of the lens is 1.5.
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
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.
A convex lens is of focal length 20 cm. Find its power.
If the lens is of focal length 25 cm. Calculate the power of the lens.
Find the power of a convex lens of focal length of + 25 cm.
Power of a lens is – 4D, then its focal length is
Increase in the converging power of eye lens cause ‘hypermetropia'
The above lens has a focal length of 10 cm. The object of height 2 mm is placed at a distance of 5 cm from the pole. Find the height of the image.
Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of –50 cm. What is the nature of the lens and its power used by each of them?
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 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?
In what unit is the power of a lens expressed?
