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प्रश्न
A student focused the Sun rays using an optical device 'X' on a screen S as shown.
From this it may be concluded that the device 'X' is a (select the correct option)
(A) Convex lens of focal length 10 cm.
(B) Convex lens of radius of curvature 20 cm.
(C) Convex lens of focal length 20 cm.
(D) Concave mirror of focal length 20 cm.
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उत्तर
Light rays from infinity are converged at the focal point of the convex lens. Therefore, the focal length of the convex lens is 20 cm.
Hence, the correct option is C.
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संबंधित प्रश्न
An image formed by a ______ mirror is always of the same size as that of the object.
Complete the following sentence:
All the distances are measured from the .......... of a spherical mirror.
The diverging lens in part (a) is replaced by a converging lens also of focal length 100 mm. The object remains in the same position and an image is formed by the converging lens. Compare two properties of this image with those of the image formed by the diverging lens in part (a).
Upto what maximum distance from the pole the image in a convex mirror can be obtained? what will be the location of object then ?
The radius of curvature of a convex mirror is 40 cm. Find its focal length.
A concave mirror forms a real image of an object placed in front of it at a distance 30 cm, of size three times the size of object. Find
- the focal length of mirror
- position of image.
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).
Define the term Focus of a concave mirror.
The distance from the pole to the focus is called ______.
