Advertisements
Advertisements
Question
What is the unit of power of a lens? Define the unit of power of a lens.
Advertisements
Solution
The unit for the power of a lens is a dioptre (D). One dioptre is the power of a lens whose focal length is 1 metre.
APPEARS IN
RELATED QUESTIONS
State power of a lens S.I. unit.
What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.
Which has more power : a thick convex lens or a thin convex lens, made of the same glass? Give reason for your choice.
A diverging lens has focal length of 3 cm. Calculate the power.
The focal length of a lens is +150 mm. What kind of lens is it and what is its power?
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.
How does the power of a lens change if its focal length is doubled?
Express the power (with sign) of a concave lens of focal length 20 cm.
Name the type of lens whose power is positive.
The image of an object formed by a lens is real, inverted and of the same size as the object. If the image is at a distance of 40 cm from the lens, what is the nature and power of the lens ? Draw ray diagram to justify your answer.
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 double convex lens has two surfaces of equal radii R and refractive index \[m = 1 \cdot 5\]
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?
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
If focal length of a convex lens is 20 cm at what is the power of the lens?
According to Rayleigh’s scattering law, the amount of scattering of light is inversely proportional to the fourth power of its ______.
Assertion and reasoning type
- Assertion: Myopia is due to the increase in the converging power of eye lens.
- Reason: Myopia can be corrected with the help of concave lens.
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.
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.
In what unit is the power of a lens expressed?
