What factors determine the critical angle in wave refraction?

The critical angle in wave refraction is determined by the refractive indices of the two media and the angle of incidence.

In more detail, the critical angle is the angle of incidence that results in the refracted wave being at 90 degrees to the normal. This is the point at which total internal reflection occurs, and the wave is reflected back into the original medium rather than being refracted into the second medium. The critical angle can only be achieved when light is travelling from a medium with a higher refractive index to one with a lower refractive index.

The refractive index of a medium is a measure of how much the speed of light is reduced when it enters that medium from a vacuum. It is calculated as the ratio of the speed of light in a vacuum to the speed of light in the medium. The greater the refractive index, the slower light travels in that medium, and the more it is refracted, or bent, when it enters or leaves the medium.

The angle of incidence is the angle between the incoming wave and the normal to the boundary at the point of incidence. The normal is a line perpendicular to the boundary. The angle of incidence is measured from the normal, not from the boundary itself.

The critical angle is given by the formula: critical angle = arcsin (n2/n1), where n1 is the refractive index of the first medium and n2 is the refractive index of the second medium. This formula shows that the critical angle depends on the ratio of the refractive indices of the two media. If the refractive index of the second medium is higher than that of the first medium, the critical angle is undefined, which means that total internal reflection cannot occur.

In summary, the critical angle in wave refraction is determined by the refractive indices of the two media and the angle of incidence. The critical angle is the angle of incidence that results in total internal reflection, and it can only be achieved when light is travelling from a medium with a higher refractive index to one with a lower refractive index.