A simple mirror will allow you to see around a corner, but to see above an object or wall, you need two mirrors aligned in a certain way. See the related link below for more information and some very helpful diagrams.
If you mean in the periscope, two.
There are no mirrors in a periscope - they use prisms. But you could use two at 45 degrees to the object and observer, parallel to one another
A periscope typically contains two mirrors - one at each end of a hollow tube. The first mirror at the top of the periscope reflects the image into the tube, and the second mirror at the bottom of the periscope reflects the image out to the viewer's eye.
A periscope works using two mirrors placed at 45 degree angles and in the direction you wish to see. A periscope uses the two mirrors to bounce light from one place to another. The light comes through the lense, bounces off one mirror to the other and then into the person's eye.
The periscope, and I believe they have a lot more than 2 mirrors.
The basic periscope uses flat mirrors, to bend and offset the optical path. If magnification is required, then the periscope will use convex objective and eyepiece lenses, becoming a refracting telescope with an offset in its optical path.
A periscope typically consists of two mirrors. The first mirror at the top of the periscope reflects light rays coming from above into the tube, while the second mirror at the bottom reflects the rays out to the observer's eyes, allowing them to see objects that are not in direct line of sight.
A simple periscope typically uses two mirrors arranged at a 45-degree angle to each other. This allows light to be reflected through the periscope, allowing the viewer to see objects around corners or over obstacles.
To make a basic periscope, you will need two small mirrors, a sturdy cardboard tube or box, scissors, tape, and a ruler. Cut the cardboard tube or box into periscope shape, attach the mirrors inside at a 45-degree angle, then use tape to secure. Adjust the mirrors until you achieve the desired reflection.
The mirrors are fitted at 45 degree angles in a periscope in the opposite directions. when you see through the periscope, the image gets reflected.
the mirrors of a periscope have gotten bigger and are easier to see out of.
A periscope uses reflection by directing light at an angle through two mirrors to view objects that are not in direct line of sight. The first mirror at the top of the periscope reflects light down, while the second mirror reflects it out to the observer, allowing them to see objects above the periscope's position.