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प्रश्न
Select the correct option:
A concave mirror is made by cutting a portion of a hollow glass sphere of radius 30 cm. The focal length of the concave mirror is:
विकल्प
24 cm
12 cm
15 cm
60 cm
उत्तर
15 cm
Explanation:
Radius of curvature = R = 30 cm
Focal length of concave mirror f = `"R"/2`
f = `30/2 = 15` cm
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संबंधित प्रश्न
Explain the following term related to spherical lenses:- optical centre
A virtual image larger than the object can be produced by a ______.
Write the formula for a lens connecting image distance (v), object distance (u) and the focal length (f). How does the lens formula differ from the mirror formula?
AB and CD, two spherical mirrors, from parts of a hollow spherical ball with its centre at O as shown in the diagram. If arc AB = `1/2` arc CD, what is the ratio of their focal lengths? State which of the two mirrors will always form virtual image of an object placed in front of it and why.
State whether the image in part (a) is real or virtual?
(a) When a concave mirror is used as a shaving mirror, where is the person's face in relation to the focus of mirror?
(b) State three characteristics of the image seen in part (a).
Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed :
(i) between the optical centre and principal focus of a convex lens.
(ii) anywhere in front of a concave lens.
(iii) at 2F of a convex lens.
State the signs and values of magnifications in the above-mentioned cases (i) and (ii).
