Question

The image formed in a periscope is :
A) Real with lateral inversion.
B) Virtual with lateral inversion.
C) Real without lateral inversion.
D) Virtual without lateral inversion.

Answer 1

Hint: A periscope is an optical instrument that uses a system of prisms, lenses, or mirrors to reflect images. A mirror is placed at a specific angle near the eye of an observer and another on another end of the periscope which sends the light of the object to the eye of the observer. The object exists in essence but not in actuality and it shows the image in virtual and the lateral inversion by two mirrors cancel each other.

Complete step by step answer:
A periscope is defined as an instrument used for observing over, around or through an obstacle or object which is prevented by direct line of sight. It consists of an outer case with the mirrors fitted at ${45^0}$ angle. These mirrors are placed parallel to the surface.
Before getting anything about the question it is important to know about the workings of a periscope. For better understanding there is a figure below:

Here, in the picture, a person is there below who wished to see another person behind the wall. He saw him with the help of the periscope.
Working of periscope:
From the diagram, we can clearly state that the image is virtual and the mirror placed parallel to each other at ${45^0}$ angle makes it laterally inverted two times. When a ray gets reflected by M1 (mirror 1) it gets shifted incident ray for M2(mirror 2) and results in a virtual image without lateral inversion. The image formed in a periscope is virtual without lateral inversion because 2 lateral inversions cancel each other.

$\therefore $The image formed in a periscope is virtual without lateral inversion. Hence option D is correct.

Note:
Uses of a periscope:
- In the military periscopes are used to observe from their hiding positions.
- Periscopes are widely used in ships and submarines to determine the distance of a torpedo or another ship and helps in deciding the right time to attack or rescue operations.
- Used in a nuclear reactor to observe the chemical reactions that are taking place inside.