Advertisements
Advertisements
प्रश्न
The power of a lens is + 0.2 D. Calculate its focal length.
Advertisements
उत्तर
Power of a lens is given by:
Power (P) =`1/f`
`f=1/p`
`f=1/0.2=5m`
APPEARS IN
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
What is the nature of a lens whose power is, −4 D?
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?
The power of a lens is +2.0D. Its focal length should be :
The power of a lens is + 1.0 D is :
Define power of a lens. Write its units. Deduce the relation `1/f =1/f_1 +1/f_2`for two thin lenses kept in contact coaxially.
Mohan obtained a sharp inverted image of a distant tree on the screen placed behind the lens. He then moved the screen and tried to look through the lens in the direction of the object. He would see:
(1) a blurred image on the wall of the laboratory.
(2) an erect image of the tree on the lens.
(3) no image as the screen has been removed
(4) an inverted image of the tree at the focus of the lens.
Consider the situation described in the previous problem. Where should a point source be placed on the principal axis so that the two images form at the same place?
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.
A convex lens is of focal length 20 cm. Find its power.
If focal length of a convex lens is 20 cm at what is the power of the lens?
Match the following:
| Column - I | Column - II | ||
| 1 | Retina | a | Path way of light |
| 2 | Pupil | b | Far point comes closer |
| 3 | Ciliary muscles | c | near point moves away |
| 4 | Myopia | d | Screen of the eye |
| 5 | Hypermetropia | e | Power of accommodation |
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.
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 ______.
The lens of power + 1·0 D is ______.
The deviation of the incident light rays produced by a lens on refraction through it is a measure of its:
When a lens is placed in a liquid, light refracts at:
