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प्रश्न
The power of the magnifying glass depends on the distance of the magnifying glass from object.
पर्याय
True
Wrong
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उत्तर
The power of the magnifying glass depends on the distance of the magnifying glass from object- Wrong
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संबंधित प्रश्न
What is meant by a power of a lens? Define its SI unit.
What does sign of power (+ve or –ve) indicate?
How unit of power related to focal length of a lens?
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.
(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.
Consider two statements A and B given below:
A: real image is always inverted
B: virtual image is always erect
Out of these two statements:
Which type of lens has (a) a positive power, and (b) a negative power?
What is the power of a convex lens of focal length 0.5 m?
What is the power of a convex lens lens whose focal length is 80 cm?
The power of a lens is + 0.2 D. Calculate its focal length.
Fill in the following blank with suitable words :
The reciprocal of the focal length in metres gives you the _________ of the lens, which is measured in ___________.
Fill in the following blank with suitable word:
For converging lenses, the power is __________ while for diverging lenses, the power is ___________.
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? Name one factor on which the power of a lens depends.
On reducing the focal length of a lens, its power ______.
How does focal length of a lens change when red light incident on it is replaced by violet light? Give reason for your answer.
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 double convex lens has two surfaces of equal radii R and refractive index \[m = 1 \cdot 5\]
A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is double of the other. Find the radii, if the refractive index of the material of the lens is 1.5.
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?
How is accommodation produced?
Which lens has more power a thick lens or a thin lens?
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
Find the power of a convex lens of focal length of + 25 cm.
If focal length of a convex lens is 20 cm at what is the power of the lens?
Increase in the converging power of eye lens cause ‘hypermetropia'
The above lens has a focal length of 10 cm. The object of height 2 mm is placed at a distance of 5 cm from the pole. Find the height of the image.
A convex lens with radii of curvature R1 = R2 is immersed in water. Assuming that the refractive indices of glass and water are 3/2 and 4/3 respectively, its focal length f1 in comparison to that in air, f, is ______.
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.
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.
An object is kept at a distance of 1m from a lens of power +2D:
- Identify the type of lens.
- Calculate its focal length and distance of the image formed.
The focal length of a double convex lens is equal to the radius of curvature of either surface. What is the refractive index of its material?
The lens of power + 1·0 D is ______.
