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प्रश्न
What do you understand by the power of a lens?
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उत्तर
The power of a lens is a measure of the degree of convergence or divergence of light rays falling on it. The power of a lens is defined as the reciprocal of its focal length in metres.
i.e., Power of lens = `1/"focal length of lens (in metres)"`
or, P = `1/f`
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संबंधित प्रश्न
What does sign of power (+ve or –ve) indicate?
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
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 power of a lens is + 0.2 D. Calculate its focal length.
What is the nature of a lens whose power is, −4 D?
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.
An object of height 4.25 mm is placed at a distance of 10 cm from a convex lens of power +5D. Find (i) the focal length of the lens, and (ii) the size of the image.
A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close contact with one another.
(a) What is the power of this combination?
(b) What is the focal length of this combination?
(c) Is this combination converging or diverging?
What is the unit of power of a lens? Define the unit of power of a lens.
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.
State the condition for the following a lens has both its focal lengths equal .
The power of a lens is + 1.0 D is :
The power of lens depends on the focal length of the lens
Assertion and reasoning type
- Assertion: Myopia is due to the increase in the converging power of eye lens.
- Reason: Myopia can be corrected with the help of concave lens.
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.
When monochromatic red light is used instead of blue light in a convex lens, its focal length will ______.
A concave lens has:
