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प्रश्न
If the radius of curvature of a concave mirror is 20 cm, its focal length is:
विकल्प
10 cm
20 cm
40 cm
80 cm
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उत्तर
10 cm
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संबंधित प्रश्न
Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray of light parallel to the principal axis of a concave mirror. Mark the angle of incidence and angle of reflection on it.
An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.
For a convex mirror, parallel rays of light appear to diverge from a point called the ______.
Define the principal focus of a concave mirror.
One of the following does not apply to a concave mirror this is:
(a) focal length is negative
(b) image distance can be positive or negative
(c) image distance is always positive
(d) height of image can be positive or negative
The diagram shows a dish antenna which is used to receive television signals from a satellite. The antenna (signal detector) is fixed in front of the curved dish.
- What is the purpose of the dish?
- Should it be concave or convex?
- Where should the antenna be positioned to receive the strongest possible signals?
- Explain what change you would expect in the signals if a larger dish was used.
A student obtained a sharp image of the grills of a window on a screen using a concave mirror. His teacher remarked that for getting better results a well lit distant object (preferably the sun) should be focussed on the screen. What should be done for this purpose?
(A) Move the screen slightly away from the mirror
(B) Move the mirror slightly towards the screen
(C) Move the screen and the mirror away from the object
(D) Move the screen and the mirror towards the object
A student has to determine the focal length of a concave mirror by obtaining the image of a distant object on a screen. For getting best result he should focus
(A) a distant tree or an electric pole
(B) a well-illuminated distant building
(C) well-lit grills of the nearest window
(D) a burning candle laced at the distant edge of the laboratory table
The radius of curvature of a concave mirror whose focal length is 5cm is ______
In the headlights of motor vehicles, ______ mirrors are used as reflectors.
