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प्रश्न
Power of a lens is – 4D, then its focal length is
विकल्प
4m
–40m
–0.25 m
–2.5 m
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उत्तर
– 0.25 m
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संबंधित प्रश्न
Ranbir claims to have obtained an image twice the size of the object with a concave lens. Is he correct? Give a reason for your answer.
The focal length of a convex lens is 25 cm. What is its power?
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?
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.
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.
Find the power of a convex lens of focal length of + 25 cm.
Match the following:
| Column - I | Column - II | ||
| 1 | Retina | a | Path way of light |
| 2 | Pupil | b | Far point comes closer |
| 3 | Ciliary muscles | c | near point moves away |
| 4 | Myopia | d | Screen of the eye |
| 5 | Hypermetropia | e | Power of accommodation |
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.
When monochromatic red light is used instead of blue light in a convex lens, its focal length will ______.
