# Relationship between incident ray and refracted

### Angle of Incidence - Incident Ray, Angle of Refraction, Snell's Law | BYJU'S The incident ray and reflected ray form two angles at the point of incidence: The relationship between the angle of incidence and angle of refraction is. The angle that the incident ray makes with the normal line is referred to as the that the difference between the angle of incidence and the angle of refraction is. Then the reflected ray makes an angle θr with this normal and lies in the same plane as the incident ray and the normal. Law of reflection: θi = θr. Specular.

When a beam of white light passes from air into a material having an index of refraction that varies with frequency, a phenomenon known as dispersion occurs, in which different coloured components of the white light are refracted at different angles, i.

The different colors correspond to different frequencies.

## Angle of Incidence

The refractive index of air depends on the air density and thus vary with air temperature and pressure. Since the pressure is lower at higher altitudes, the refractive index is also lower, causing light rays to refract towards the earth surface when traveling long distances through the atmosphere.

This shifts the apparent positions of stars slightly when they are close to the horizon and makes the sun visible before it geometrically rises above the horizon during a sunrise.

Heat haze in the engine exhaust above a diesel locomotive. Temperature variations in the air can also cause refraction of light. This can be seen as a heat haze when hot and cold air is mixed e. This makes objects viewed through the mixed air appear to shimmer or move around randomly as the hot and cold air moves. This effect is also visible from normal variations in air temperature during a sunny day when using high magnification telephoto lenses and is often limiting the image quality in these cases.

### The Angle of Refraction

Mirage over a hot road. Air temperature variations close to the surface can give rise to other optical phenomena, such as mirages and Fata Morgana. A comparison of the angle of refraction to the angle of incidence provides a good measure of the refractive ability of any given boundary. For any given angle of incidence, the angle of refraction is dependent upon the speeds of light in each of the two materials. The speed is in turn dependent upon the optical density and the index of refraction values of the two materials. There is a mathematical equation relating the angles that the light rays make with the normal to the indices plural for index of refraction of the two materials on each side of the boundary. This mathematical equation is known as Snell's Law and is the topic of the next section of Lesson 2.

Snell's law of Refraction

We Would Like to Suggest Why just read about it and when you could be interacting with it? Interact - that's exactly what you do when you use one of The Physics Classroom's Interactives. Now consider wave fronts and their corresponding light rays approaching the surface at an angle. We can see that the rays will bend as the wave passes from air to glass. The bending occurs because the wave fronts do not travel as far in one cycle in the glass as they do in air.

As the diagram shows, the wave front halfway into the glass travels a smaller distance in glass than it does in air, causing it to bend in the middle. Thus, the ray, which is perpendicular to the wave front, also bends. The situation is like a marching band marching onto a muddy field at an angle to the edge of the field. The rows bend as the speed of the marchers is reduced by the mud.

The amount of bending depends on the angle of incidence and on the indices of refraction of glass and air, which determine the change in speed. This is Snell's law, or the law of refraction. When light passes from one transparent medium to another, the rays are bent toward the surface normal if the speed of light is smaller in the second medium than in the first. The rays are bent away from this normal if the speed of light in the second medium is greater than in the first.

The picture on the right shows a light wave incident on a slab of glass.