Advertisements
Advertisements
प्रश्न
Find the power of a convex lens of focal length of + 25 cm.
Advertisements
उत्तर
Given: Focal length (f) = 25 cm = 0.25 m
To find: Power of the lens (P)
Formula: P = `1/("f"("m"))`
Calculation: From formula, P = `1/0.25` = 4 D
The power of the convex lens is 4 D.
APPEARS IN
संबंधित प्रश्न
Calculate the focal length of a corrective lens having power +2D.
What is meant by a power of a lens? Define its SI unit.
Define the power 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.
Find the focal length of a lens of power −2.0 D. What type of lens is this?
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?
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.
The lens mentioned in 6(b) above is of focal length 25cm. Calculate the power of the lens.
What can you see in a completely dark room? If you switch on an electric bulb in this dark room as a light source, explain how you could now see:
(a) the electric bulb
(b) a piece of white paper
Name the physical quantity whose unit is dioptre.
The focal length of a convex lens is 25 cm. What is its power?
What is the power of a convex lens lens whose focal length is 80 cm?
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?
Fill in the following blank with suitable word:
For converging lenses, the power is __________ while for diverging lenses, the power is ___________.
What is the unit of power of a lens? Define the unit of power of a lens.
A diverging lens has a focal length of 0.10 m. The power of this lens will be:
How is the sign (+ or -) of power of a lens related to its divergent or convergent action?
Express the power (with sign) of a concave lens of focal length 20 cm.
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 normal eye is not able to see objects closer than 25 cm because
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?
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
A lens forms an upright and diminished image of an object, irrespective of its position. What kind of lens is this? Draw an outline ray diagram to show the formation of the image. State the position and one more characteristic of the image.
A stick partly immersed in water appears to be bent. Draw a ray diagram to show the bending of the stick when placed in water and viewed obliquely from above.
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.
According to Rayleigh’s scattering law, the amount of scattering of light is inversely proportional to the fourth power of its ______.
Increase in the converging power of eye lens cause ‘hypermetropia'
When monochromatic red light is used instead of blue light in a convex lens, its focal length will ______.
The power of convex lens of focal length 20 cm is ______.
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.
In what unit is the power of a lens expressed?
