The critical angle is the angle at which a ray of light is no longer refracted but completely reflected. True or false?
True.
To understand why this is true, we need to review some concepts related to the refraction of light. When a ray of light passes from one medium to another, such as from air to water or from air to glass, it changes direction due to a change in the speed of light. This change in direction is called refraction.
The angle at which refraction occurs depends on the angle at which the light ray strikes the boundary between the two media, as well as the refractive indices of the two media. The refractive index is a measure of how much a medium can bend or slow down light. It is a dimensionless quantity and is usually denoted by the symbol "n".
However, when the light ray strikes the boundary at a certain angle, known as the critical angle, something interesting happens. Instead of being refracted, the light ray gets reflected back into the original medium. This phenomenon is called total internal reflection.
The critical angle can be calculated using the formula:
Critical angle = sin^(-1)(n2 / n1),
Where n1 is the refractive index of the medium in which the incident ray is traveling, and n2 is the refractive index of the medium on the other side of the boundary.
So, in summary, the critical angle is the angle at which a ray of light is no longer refracted but completely reflected.