# Reflection Coefficient

## Definition - What does Reflection Coefficient mean?

Reflection Coefficient is the amount of energy that is reflected when an incident light or radiation falls on the surface of a material. It is associated with geophysics and can be expressed as a ratio of amplitude of a reflected wave to the incident wave. At times it is also referred to as reflectivity and is used when seismic studies have to be performed.

## Petropedia explains Reflection Coefficient

Reflection coefficient is used in feeder testing for the reliability of the medium. In the field of optics and microwave radiations, the reflection coefficient can either refer to the reflectance or the amplitude of the reflected wave.

In general, reflection coefficient (R) is represented by the equation below:

R = (d_{2}V_{2} – d_{1}V_{1}) / (d_{2}V_{2} + d_{1}V_{1}), where,

d_{1} & d_{2} represent the density of medium 1 and medium 2 respectively.

V_{1} & V_{2} represent the velocity of medium 1 and medium 2 respectively.

The value for reflectivity coefficient:

- For water to air is -1. This means that almost all amount of energy is reflected in these two mediums.
- For water to rock is 0.5.
- For shale to sand is 0.2.