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Vimal Raj asks:
“A thick plane mirror forms a number of images of a point source of light . which image is brightest ?”
Answer: In the case of a thick plane mirror, reflection takes place at the two surfaces, (top and bottom surfaces) and images are formed due to both. The second surface is silvered and therefore the second image is the brightest. Further images are formed due to multiple reflections and due to absorption of light by medium the images become fainter.
If the front surface of the mirror is silvered, only one image will be formed.
John Abraham asks:
I am having trouble with a problem.
Q. In an experiment to determine the focal length (f) of a concave mirror by the u–v method, a student places the object pin A on the principal axis at a distance x from the pole P. The student looks at the pin and its inverted image from a
distance keeping his/her eye in line with PA. When the student shifts his/her eye towards left, the image appears to the right of the object pin. Then
(A) x < f
(B) f < x < 2f
(C) x = 2f
(D) x > 2f
The answer is B
(Try giving your explanation as comment. If not satisfied, ask again)
The image and the object will move together at 2f
The one closer to the eye will move faster
In the question, the situation occurs when the image is closer to the eye and this happens when the object is between f and 2f
Hence the answer is B