If the prism is small enough, less light energy would lost compared to a mirror. Therefore, prisms are used in periscopes to make the image sharp and clear instead of a mirror.
2. Fiber optic
The core which is of diameter of around 10µm has a cladding of whose refractive index is higher than the core. Total internal reflection occurs on the edge an the light bounces. Hence, light is transmitted from one end to another.
3. Rain Sensor
An infrared light (sunlight) is beamed at a 45-degree angle into the windshield from the interior — if the glass is wet, less light makes it back to the sensor, and the wipers turn on.