What is a periscope? Draw a neat ray diagram to show the working of a periscope?

1. A periscope is defined as an instrument used for observing over, around, or through an obstacle or object which is prevented by a direct line of sight.
2. Its working is based on the laws of reflection.
3. It consists of an outer case with mirrors at each end at ${45}^{°}$ angle, these mirrors are placed parallel to the surface.