Question

The final image formed in a periscope is:
A. Both real and virtual
B. Reflected
C. Real
D. None of these

Answer 1

Hint: A simple periscope is just a long tube with a mirror at each end. The mirrors are fitted into each end of a tube at an angle of exactly 45 degrees so that they face each other.

Complete step by step solution:
A simple periscope is just a long tube with a mirror at each end. The mirrors are fitted into each end of a tube at an angle of exactly 45 degrees so that they face each other.
In the periscope, light hits the top mirror at 45 degrees and reflects away at the same angle. The light bounces down to the bottom mirror. When that reflected light hits the second mirror it is reflected again at 45 degrees, and finally right into our eye.
Light is always reflected away from a mirror at the same angle that it hits the mirror.

Hence, the image formed in a periscope is reflected, and therefore is not real. Option B is correct.

Additional information:
A periscope is an optical instrument used for viewing objects that are above the level of direct sight or in an otherwise obstructed field of vision, consisting essentially of a tube with an arrangement of prisms or mirrors. A periscope is usually used to see objects ahead or behind in submarines.

Note: Before solving the sum students need to be able to understand the working and meaning of periscopes and at what angles in the periscope the mirrors are placed.