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प्रश्न
Focal length : metre : : power of lens : _______
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उत्तर
Focal length : metre : : power of lens : dioptre
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संबंधित प्रश्न
What is meant by a power of a lens? Define its SI unit.
How unit of power related to focal length of a lens?
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
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.
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.
What is the nature of a lens whose power is, −4 D?
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 lens has a focal length of, −10 cm. What is the power of the lens and what is its nature?
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.
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?
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 do you understand by the power of a lens?
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.
A converging lens has a focal length of 50 cm. The power of this lens is:
A diverging lens has a focal length of 0.10 m. The power of this lens will be:
Define the term focal length of a lens.
State the condition for the following a lens has both its focal lengths equal .
How is the sign (+ or -) of power of a lens related to its divergent or convergent action?
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 symmetric double convex lens is cut in two equal parts by a plane containing the principal axis. If the power of the original lens was 4 D, the power of a divided lens will be
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.
A convex lens produces a double size real image when an object is placed at a distance of 18 cm from it. Where should the object be placed to produce a triple size real image?
A diverging lens of focal length 20 cm and a converging lens of focal length 30 cm are placed 15 cm apart with their principal axes coinciding. Where should an object be placed on the principal axis so that its image is formed at infinity?
Which lens has more power a thick lens or a thin 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.
If there is a convex lens of focal length 75 cm and a concave lens of focal length 40 cm, then calculate their combined power and combined focal length.
If focal length of a convex lens is 20 cm at what is the power of the lens?
Power of a lens is – 4D, then its focal length is
The power of lens depends on the focal length of the lens
The focal length of a concave lens is 20 cm. The focal length of a convex lens is 25 cm. These two are placed in contact with each other. What is the power of the combination? Is it diverging, converging or undeviating in nature?
An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is
- negative and
- positive.
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 power of convex lens of focal length 20 cm is ______.
The lens of power + 1·0 D is ______.
