Translations of Encyclopedia about Physics

Reflection of Light

The reflection of light is when a wave of light does not pass through the boundary surface between two optical environments but rather reflects back into the space of the originating environment.

With certain exceptions (refer below), each object onto which light rays fall reflects light. However, the object absorbs a portion of the light rays. The greater the reflection and lesser the absorption of light, the clearer we are able to view the object. Only once the reflected light arrives to us do we actually see the object. Without the physical characteristic of light reflection, we would not be able to see at all. The clearest example of how light reflection allows us to see is glass.

Light reflection always occurs according to the same laws. The intensity of reflected light rays and their direction depends on the density of the surface of the object reflecting the light. An object’s surface changes the direction of a light ray while the density of the material it is made from affects the intensity of the reflection.

Light reflection can be explained easily when looking at the moon. The light we see from the moon is made of sun rays which fall on it and reflect back to us. We notice various phases of the moon depending on which part of the moon light from the sun is cast on. During a full moon, light from the sun reflects off that portion of the moon which faces us. During a new moon however, light from the sun is cast on the opposite side of the sun (the side we do not see). Therefore, how we perceive the moon depends on its position relative to the earth and the sun.

Glass has a low reflecting coefficient, for which reason it is transparent and why it may seem invisible. If glass is coloured with heterogeneous material, its reflective quality increases and the degree of its transparency decreases. An example of this is lead or flint glass.

According to existing knowledge, there is only one case where there is absolutely no reflection of light, and that is with black holes. Black holes have such a large mass and weight that they absorb all forms of electromagnetic radiation, including light, because the gravity of the object within it is so strong that such forms of radiation cannot escape it.

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