In a periscope, the two plane mirrors are kept
parallel to each other
Periscope Mirror Arrangement Explained
A periscope is a device used to see objects that are obstructed from direct view, typically by using a system of mirrors or prisms. It allows observation around corners, over obstacles, or from a concealed position, like in submarines or tanks.
Functioning of a Periscope
The basic principle of a simple periscope relies on two main components: two plane mirrors and a light-proof tube connecting them.
- Light from the distant object enters the top of the periscope tube.
- This light strikes the first plane mirror, which is positioned at an angle.
- The first mirror reflects the light downwards along the tube.
- The light then travels down the tube and strikes the second plane mirror.
- This second mirror is positioned parallel to the first mirror and reflects the light horizontally towards the observer's eye.
Mirror Orientation in Periscopes
The effectiveness of a periscope depends entirely on the precise orientation of its mirrors. Key points include:
- Parallel Mirrors: For the light to be redirected correctly and allow the observer to see the object clearly, the two plane mirrors must be set parallel to each other.
- Angle Setting: Each mirror is typically tilted at an angle of 45 degrees (\(\mathit{45^\circ}\)) relative to the direction the tube is pointing. The top mirror reflects light downwards, and the bottom mirror reflects it outwards to the observer. This setup effectively redirects the line of sight by 180 degrees.
The parallel arrangement ensures that the light path is continuous and results in an upright image for the observer.
Evaluating Other Mirror Arrangements
Considering alternative arrangements highlights why the parallel configuration is essential:
- Perpendicular Mirrors: If the mirrors were placed perpendicular (\(\mathit{90^\circ}\)) to each other, the light would be reflected only once at a right angle, which wouldn't allow viewing around corners or obstacles effectively in the manner a periscope does.
- Other Angles: Placing the mirrors at angles like \(\mathit{60^\circ}\) or other angles that are not parallel would disrupt the required light path. The image might be distorted, inverted incorrectly, or simply not visible to the observer.
Summary of Mirror Placement
In conclusion, the standard and functional design of a periscope requires its two plane mirrors to be positioned parallel to each other, typically angled at \(\mathit{45^\circ}\) to the vertical axis of the tube, enabling the observation of objects not in the direct line of sight.
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