A concave mirror is used to form an image of the sun on a white screen...
If lower half (or a part) of a mirror is covered with a black paper then complete image of the object will be formed as before. However, the image will be less bright now.
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A concave mirror is used to form an image of the sun on a white screen...
Correct answer is A because even if we cover the lower part of the mirror with a black paper the image will be form but the brightness of the image would be less.
A concave mirror is used to form an image of the sun on a white screen...
Explanation:
When a concave mirror is used to form an image of the sun on a white screen, the image formed is highly bright. If the lower half of the mirror is covered with a black paper, the following effects will be observed:
Reduction in brightness:
When the lower half of the concave mirror is covered with black paper, the amount of light falling on the mirror reduces. As a result, the amount of light reflected by the mirror also reduces. Hence, the image formed on the screen will be less bright than before.
No effect on focal length:
The focal length of the concave mirror will remain the same even if the lower half of the mirror is covered with black paper. Hence, the image formed on the screen will still be focussed.
No change in size:
The size of the image formed on the screen depends on the distance between the mirror and the screen. It is not affected by the black paper covering the lower half of the mirror. Hence, the image formed on the screen will be of the same size as before.
Partial image formation:
When the lower half of the concave mirror is covered with black paper, the light rays falling on that portion of the mirror will not be reflected towards the screen. Hence, the lower half of the image formed on the screen will disappear.
Therefore, the correct answer is option A, which states that the image formed on the screen will be less bright than before when the lower half of the concave mirror is covered with black paper.