Question

A number of images of candle flame can be seen in a thick mirror. The brightest image is:
A. The first one
B. The second one
C. The third one
D. The last one

Answer 1

Hint:Several faint images and one bright image of the flame forms in the thick plane mirror. This is due to the partial reflection at the first surface and actual reflection at the last surface of the glass mirror. The brightness of the flame depends on the intensity of light.

Complete answer:
When we observe the image of the candle flame in the plane mirror of thick glass, we see several faint images and one bright image of the candle flame. This is due to the partial reflection at the first surface and actual reflection at the last surface of the glass mirror.

When the light ray incident on the surface of the flat thick mirror, it undergoes partial reflection and refraction. Thus, some fraction of the light gets reflected at the first surface and enters our eye. The intensity of this light is very small. Now, the refracted light also reflects at the second surface where the back side of the mirror is completely blackened.

Therefore, the light gets completely reflected at the second surface and the intensity of this light is comparatively greater than the intensity of light reflected that the first surface. So, the image of the candle flame reflected from the second surface is the brightest.

The images formed after the second image is from the multiple reflections between the two surfaces of the flat mirror. Since the intensity of the light gets reduced with each reflection, the images after the second image are relatively dimmer than the second one.

So, the correct answer is option B.

Note: In case of the thin mirror, a single image will be formed by the mirror since there is no other reflecting surface. The images formed after the second image are relatively dimmer than the first image since most of the light will refract at the first surface.