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प्रश्न
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
उत्तर
We cannot see anything in a dark room as there is no light present.
(a) We see the electric bulb because it produces light that reaches our eyes directly.
(b) We see a piece of white paper due to the diffused reflection of light from the surface of the paper.
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संबंधित प्रश्न
How unit of power related to focal length of a lens?
Find the focal length of a lens of power −2.0 D. What type of lens is this?
Which type of lens has (a) a positive power, and (b) a negative power?
What is the nature of a lens whose power is, −4 D?
Define the term focal length of a lens.
On reducing the focal length of a lens, its power ______.
A symmetric double convex lens in cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power a cut-lens will be
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.
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 |
The power of convex lens of focal length 20 cm is ______.
