General Knowledge - Basic General Knowledge - Discussion

Periscopes allow a submarine, when submerged at a relatively shallow depth, to search visually for nearby targets and threats on the surface of the water and in the air. When not in use, a submarine's periscope retracts into the hull.

A submarine commander in tactical conditions must exercise discretion when using his periscope, since it creates a visible wake (and may also become detectable by radar[citation needed]), giving away the sub's position.

Kaleidoscope is a circle of mirrors containing loose, colored objects such as beads or pebbles and bits of glass. As the viewer looks into one there are three rectangular lengthwise mirrors. Setting the mirrors at a 45-degree angle creates eight duplicate images of the objects, six at 60 deg, and four at 90 degrees.

As the tube is rotated, the tumbling of the coloured objects presents the viewer with varying colours and patterns. Any arbitrary pattern of objects shows up as a beautiful symmetrical pattern created by the reflections in the mirrors. A two-mirror model yields a pattern or patterns isolated against a solid black background, while a three-mirror (closed triangle) model yields a pattern that fills the entire field.

What is periscope?

What is kaleidoscope and sprectoscope?

Good information, thanks all.

Thanks all for giving explanation for the answer.