In optics, angle of incidence can be defined as the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence (called as normal). To understand the angle of incidence, we have to first look into the concept of reflection of light. We all know that when a ray of light hits a polished surface like a mirror it is reflected back.
Here are some key points to make you understand the concept of angle of incidence easily.
- The ray of light that hits the polished surface is called the incident ray.
- The ray that gets reflected away is called the reflected ray.
- The point at which the light hits the surface is called the point of incidence.
- If a line is drawn perpendicular to that point, it is called the normal.
What is Angle of Incidence?
The incident ray and reflected ray form two angles at the point of incidence:
- The angle formed between the normal and the incident ray at the point of incidence is called the angle of incidence.
- Similarly, the angle formed between the normal and the reflected ray at the point of incidence is called the angle of reflection.
Angle Of Incidence Formula
Angle of incidence is equal to the reflected angle through the law of reflection. The angle of incidence and the angle of reflection is always equal and they are both on the same plane along with the normal.
What is the relationship between angle of incidence and angle of refraction?
When light passes from one medium to another with different densities, its path gets deviated. This phenomenon is called the refraction of light. Like a reflection, there are similar components in refraction too. They are:
- Incident ray
- Refracted ray
- Point of incidence
The angle formed at the point of incidence between the incident ray and the normal is called the angle of incidence. And the angle formed between the refracted ray and the normal is called the angle of refraction.
The relationship between the angle of incidence and angle of refraction is explained by Snell’s law, which states that ratio of the sine of the angle of refraction and the sine of the angle of incidence is always constant and equivalent to the ratio of phase velocities of the two mediums it is passing through.