Advertisements
Advertisements
प्रश्न
Find the power of a concave lens of focal length 2m.
Advertisements
उत्तर
The focal length of a concave lens, f = 2m
Power of lens,
P = `1/f`
= `1/(-2)`
= -0.5D
Hence power of the lens = – 0.5 D
APPEARS IN
संबंधित प्रश्न
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
(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.
Which one of the following materials cannot be used to make a lens?
What is the nature of a lens whose power is, −4 D?
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?
What is the unit of power of a lens? Define the unit of power of a lens.
A converging lens has a focal length of 50 cm. The power of this lens is:
Express the power (with sign) of a concave lens of focal length 20 cm.
How does focal length of a lens change when red light incident on it is replaced by violet light? Give reason for your answer.
A thin converging lens is formed with one surface convex and the other plane. Does the position of image depend on whether the convex surface or the plane surface faces the object?
Complete the diagram to show the formation of the image of the object AB.
(i) Name the Lens LL’.
(ii) Where is the image of the object AB formed?
(iii) State three characteristics of the image.
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?
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?
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 ______.
In what unit is the power of a lens expressed?
