It depends on the submarine. If measure the distance from the top a fully extended periscope to the bottom of the boat you will get the "Depth of the Keel" at which the periscope is out of the water. Generally between 30 feet and 70 feet.
Yes sonar can be used at periscope depth. Surface ships also have sonar arrays on them. They are usually used to detect submarines.
A periscope.
Google it for the diagram and u will understand why.
To see over walls and in submarines
A Periscope or Radar
periscope
On the newer class submarines that don't employ optics, they're called "Photonics Masts". But it's still a Periscope.
PERISCOPE
They use Radar , Sonar, and at periscope depth- optical range finders, the tech manual for the latter is over 300 pages, so its a skilled craft to operate these specialized sights.
The periscope was invented in the 19th century in England by Sir Howard Grubb. It was further developed and utilized in submarines for navigation and observation underwater.
The periscope was invented in 1450 by Johann Gutenberg.
The Captain used the periscope to locate the enemy ships.A periscope is the eye of a submarine.