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प्रश्न
State the condition of the following:
A lens has both its focal lengths equal.
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उत्तर
If the medium on both sides of the lens is same, the first and second focal lengths are equal.
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संबंधित प्रश्न
What is a lens?
Distinguish between a real and a virtual image.
Study the diagram shown in Fig. 5.56
Where is the image formed?
The diagram given below shows the position of an object OA in relation to a converging lens whose foci are at F1 and F2.
Describe three characteristic of the image.
For an object placed at a distance 20 cm in front of a convex lens, the image is at a distance 20 cm behind the lens. The focal length of the convex lens is ______.
In the following diagram the object and the image formed by the respective lenses are shown. Complete the ray diagram, and locate the focus. Find the focal length of the lens.
Make the correct choices in the following items :
The image formed by a diverging lens, shown in fig, , is
(a)A ray of light is incident at 45° on the face of
(i) A rectangular block of glass.
(ii) A 600 glass prism.
(b) Draw a sketch showing how the ray of monochromatic ray of light passes through glass in each case.
(c) With the aid of a diagram, explain how the face of a right angled prism may totally reflect incident on it.
(d) A thick plane mirror produces several faint images in addition to a prominent one. Draw a ray diagram showing how reflection and refraction produce all these images.
(e) Fig. represents a stone S at the bottom of a pond of water. Using the two rays, as shown, complete the ray diagram to show where the image of the stone appears when viewed from E.
(f) What is a''mirage'? Explain with the help of a diagram.
(g) A man observes the bottom of a swimming pool of 3 m depth. If the refractive index of water is 1.3, what is the apparent depth of water?
(h) When a ray of light undergoes refraction through a glass slab and when it emerges it is displaced laterally (Fig). What are the factors on which the lateral displacement depends?
(i) Fig. shows three rays of light OA, OB and OC passing from water to air, making angles 490, 410 and 350 with the horizontal surface respectively. Draw an approximate path of the emergent ray for each. (Critical angle of water is 490.)
How will you differentiate between a convex and a concave lens by looking at a distant object.
