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प्रश्न
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?
उत्तर
Positive power indicates it is a converging lens.
Power of a lens is given by:
power(p)=`1/f`
`0.5=1/f`
`f=1/0.5`
`f=2m`
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संबंधित प्रश्न
State power of a lens S.I. unit.
Which of the two has a greater power: a lens of short focal length or a lens of large focal length?
What is the power of a convex lens of focal length 0.5 m?
The power of a lens is + 1.0 D is :
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.
Surabhi from std. X uses spectacle. The power of the lenses in her spectacle is 0.5 D.
Answer the following questions from the given information:
- Identify the type of lenses used in her spectacle.
- Identify the defect of vision Surabhi is suffering from.
- Find the focal length of the lenses used in her spectacle.
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
If the lens is of focal length 25 cm. Calculate the power of the lens.
The power of lens depends on the focal length of the lens
The power of convex lens of focal length 20 cm is ______.
