Which one of the following is the natural phenomenon based on which a simple periscope works ?

A simple periscope is an optical instrument that allows an observer to see objects that are not in their direct line of sight, such as over obstacles or from a submerged submarine [1]. It operates primarily on the principle of the reflection of light. In its simplest construction, a periscope consists of a Z-shaped tube containing two plane mirrors placed parallel to each other and oriented at a 45-degree angle to the path of light [1]. Light from an object strikes the first mirror and is reflected at a 90-degree angle toward the second mirror, which reflects it again into the observer's eye. While advanced periscopes in submarines may use prisms to achieve total internal reflection for better image quality, the fundamental natural phenomenon governing a simple periscope is the basic law of reflection [1].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 11: Light: Shadows and Reflections > 11.8.1 Periscope > p. 164