Light Amplification by stimulated Emission of Radiation . Heat is also generated as a by product.
Mirrors are specular devices that can change the direction a light beam.
Polished on the specular surface causes regular reflection and the image of the luminous source is sharply defined. A plane mirror of the plate glass is silvered on one surface to reflect the light efficiently. When a ray enters the dense medium at an oblique angle. Refraction does occur and the ray is bent toward normal. The density of a material is determined by the speed of light through the material.