A periscope uses two plane mirrors inclined at 45°. 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?

A periscope typically consists of two parallel plane mirrors inclined at 45° to the path of light. The image formation in a periscope is governed by the laws of reflection, which state that the angle of incidence is equal to the angle of reflection (θi = θr). These laws are independent of the refractive index of the medium surrounding the mirrors.

When the tube is filled with a transparent liquid (refractive index 1.5), the speed of light decreases within the tube, but the geometric path of the light rays remains the same. Since plane mirrors always produce a virtual image of the same size and orientation as the object, and the two-mirror system cancels out the lateral inversion, the final image remains unchanged in terms of its size, orientation, and nature. While there might be a negligible change in brightness due to reflection at the entry/exit interfaces, it does not follow a "1.5 times" ratio, making option A the most accurate.