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प्रश्न
An optical device has been given to a student and he determines its focal length by focusing the image of the sun on a screen placed 24 cm from the device on the same side as the sun. Select the correct statement about the device.
(A) Convex mirror of focal length 12 cm
(B) Convex lens of focal length 24 cm
(C) Concave mirror of focal length 24 cm
(D) Convex lens of focal length 12 cm
उत्तर
The optical device is a concave mirror because when light rays from a distant object (here it is Sun) fall on this mirror, its image is formed at the focus of the mirror on the same side as the object. Thus in the given case, distance between the mirror and the screen is the focal length of the concave mirror. Hence, the focal length of the given device (concave mirror) is 24 cm.
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संबंधित प्रश्न
A student obtained on a screen the sharp image of a candle flame placed at the farther end of laboratory table using a concave mirror. For getting better value of focal length of the mirror, the teacher suggested to him to focus the sun. What should the student do?
(A) Should move the mirror away from the screen.
(B) Should move the mirror towards the screen.
(C) Should move the mirror and screen both towards the sun.
(D) Should move only the screen towards the sun.
In each case (a) and (b), draw reflected rays for the given incident rays and mark focus by the symbol F.
What do you understand by the term real image?
In the following figure shows a concave mirror with its pole (P), focus (F) and centre of curvature (C). Draw a ray diagram to show the formation of the image of an object AB by the concave mirror.
Complete the following diagrams shown in the following figures by drawing the reflected rays.
Define the term Principle focus.
The spherical mirror used in a beauty parlour as make-up mirror is _______.
