Question

Explain the nature of the image formed in a periscope.

Answer 1

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. It consists of an outer case with plane mirrors at each end at a $45°$ angle.
3. These mirrors are placed parallel to the surface.

Characteristics of the image formed by a Periscope:

1. The image developed by plane mirrors used inside the periscope is virtual and laterally inverted.
2. When a ray reflected by the first plane mirror shifts the incident ray for the second one, this laterally inverted incident ray gets reflected by the second plane mirror and reaches the eyes as an image of an object without lateral inversion.
3. Thus, It results in a virtual image without lateral inversion because two lateral inversions cancel each other.
4. The diagrammatic representation of the rays of light reaching from object to eye when an object is seen from a periscope is given below:

Other Uses of a Periscope:

1. Used in submarines to determine the distance of a torpedo and helps in deciding the right time for the attack.
2. Used in a nuclear reactor to observe the chemical reactions that are taking place.
3. In the military, periscopes are used to observe from their hiding position.

Therefore, an image formed in a periscope is virtual and without lateral inversion.