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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
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.
The lens mentioned in 6(b) above is of focal length 25cm. Calculate the power of the lens.
Give the usual name for the following:
A point inside a lens through which the light passes undeviated.
Which one of the following materials cannot be used to make a lens?
Which of the two has a greater power: a lens of short focal length or a lens of large focal length?
What is the nature of a lens whose power is, −4 D?
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?
How does focal length of a lens change when red light incident on it is replaced by violet light? Give reason for your answer.
Consider three converging lenses L1, L2 and L3 having identical geometrical construction. The index of refraction of L1 and L2 are \[\mu_1 \text{ and } \mu_2\] respectively. The upper half of the lens L3 has a refractive index \[\mu_1\] and the lower half has \[\mu_2\] following figure . A point object O is imaged at O1 by the lens L1 and at O2 by the lens L2placed in same position. If L3 is placed at the same place,
(a) there will be an image at O1
(b) there will be an image at O2.
(c) the only image will form somewhere between O1 and O2
(d) the only image will form away from O2.
