How does a periscope work if you add more mirrors?
General knowledgeAsked by Anonymous23 Oct 2026, 11:18 AM ISTUpdated
In one line
A periscope with more mirrors lets you see around more corners or over longer distances, but each mirror changes the path of light.
Periscope — Instrument for observation from a concealed position A real periscope, showing how mirrors are placed inside to reflect light. Image: Wikipedia
The rule
A periscope uses mirrors placed at angles to reflect light so you can see objects that are not in your direct line of sight.
The main rule: Light bounces off a mirror at the same angle it hits it (the law of reflection).
Let's understand it simply
Imagine you are hiding behind a wall and want to see what is on the other side. A basic periscope uses two mirrors, each at a 45° angle. Light from the object hits the top mirror, bounces down to the bottom mirror, and then into your eye. If you add more mirrors, the light keeps bouncing from one to the next. This lets you make the periscope longer, or even bend it around corners, like a pipe with mirrors inside.
How it works
Light from the object enters the periscope and hits the first mirror.
The mirror reflects the light at a 90° turn (if placed at 45°).
If there is a second mirror, the light hits it and turns again.
Each extra mirror can change the direction, letting you look around more bends.
The final mirror sends the light into your eye, so you see the object.
How light travels in a periscope with 3 mirrors
Light enters the top opening.
Hits the first mirror at 45°, turns down.
Hits the second mirror at 45°, turns sideways.
Hits the third mirror at 45°, turns towards the eye.
The story behind it
Periscopes were first used in submarines and by soldiers in trenches, to see without being seen. The idea is based on the simple property of mirrors reflecting light. The more mirrors you add, the more you can change the viewing direction.
Where you see it in real life
Submarines: Periscopes with many mirrors let sailors see above water while staying hidden.
Army bunkers: Soldiers use periscopes to look over walls without exposing themselves.
Science toys: Kids' periscopes often have more than two mirrors for fun shapes.
Inspection tools: Mechanics use periscopes with extra mirrors to look inside engines.
Why it matters
Lets you see over, under, or around obstacles without moving.
Used in defense, science, and engineering.
Shows how light travels and reflects, a key idea in optics.
Helps in designing cameras, telescopes, and other optical devices.
Common mistakes
Thinking more mirrors always make the image clearer (actually, every mirror can make it dimmer).
Placing mirrors at the wrong angle—if not at 45°, the image will not travel straight.
Forgetting that each mirror flips the image direction.
Remember it
More mirrors = more turns for light, but also a dimmer image and more chances for mistakes.
Check yourself
What happens to the image if you add more mirrors to a periscope?
The image can be seen around more corners, but it becomes dimmer.
Why must the mirrors in a periscope be at 45° angles?
So the light turns 90° at each mirror and reaches your eye correctly.
If you use four mirrors in a periscope, what is one possible use?
To look around two corners, like in a zig-zag pipe.
Why does the image get dimmer with more mirrors?
Because each mirror absorbs a little light, so less light reaches your eye.
Quick recap
Each mirror in a periscope changes the direction of light.
Adding more mirrors lets you see around more bends or corners.
Too many mirrors make the image dimmer.
Mirrors must be at the correct angle (usually 45°) for the periscope to work.
