A periscope uses two plane mirrors inclined at 45^\circ. If the tube of the periscope is filled with a complete transparent liquid of refractive index 1.5, then which one of the following is correct in respect of the image seen?

  1. A. The image will remain unchanged.
  2. B. The image will appear laterally shifted.
  3. C. The image will appear 1.5 times brighter.
  4. D. The image will appear 1.5 times darker.

Correct Answer: A. The image will remain unchanged.

Explanation

The laws of reflection at the plane mirrors are independent of the surrounding medium's refractive index. As long as light enters and exits normally to the tube ends, the image position remains essentially unchanged.

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