Submarines

The submarines sank a lot of ships.

Passive sonar systems are used primarily to detect noise from marine objects (such as submarines or ships) and marine animals like whales.

Does Algeria need submarines?

How many submarines does Algeria have?

He looked at the two enemy submarines through the periscope. They were in danger and he knew it, but how were they going to escape from them?

How many submarines does the Algerian navy have?

For the first time in history, three Russian nuclear-powered submarines are breaking the ice and floating to the surface at the same time.

China has the most submarines.

Large submarines have small windows.

A periscope is an optical instrument that uses a system of prisms, lenses or mirrors to reflect images through a tube. Light from a distant object strikes the top mirror and is then reflected at an angle of 90 degrees down the periscope tube. At the bottom of the periscope, the light strikes another mirror and is then reflected into the viewer’s eye. This simple periscope uses only flat mirrors as compared to the periscopes used on submarines, which are usually a complex optical system using both lenses and mirrors.