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प्रश्न
A student used a device (X) to obtain/focus the image of a well illuminated distant building on a screen (S) as shown below in the diagram. Select the correct statement about the device (X).
पर्याय
This device is a concave lens of focal length 8 cm.
This device is a convex mirror of focal length 8 cm.
This device is a convex lens of focal length 4 cm.
This device is a convex lens of focal length 8 cm.
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उत्तर
This device is a convex lens of focal length 8 cm.
Explanation:
The incident rays after passing through the lens converge at the focus. So, the device 'X' is a converging or a convex lens. The distance between the lens and the screen gives the focal length of the lens.
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संबंधित प्रश्न
A ray of light is incident normally on a plane mirror. What will be the
angle of reflection?
Draw suitable diagrams to illustrate the action of (i) concave mirror and (ii) convex mirror on a beam of light incident parallel to the principal axis.
Name the kind of mirror used to obtain:
A real and diminished image.
A point light source is kept in front of a convex mirror at a distance of 40 cm. The focal length of the mirror is 40 cm. Find the 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).
Size of image of an object by a mirror having a focal length of 20 cm is observed to be reduced to 1/3rd of its size. At what distance the object has been placed from the mirror? What is the nature of the image and the mirror?
What is the focal length (f) of a mirror?
