Why does refraction occur?
Refraction occurs when light passes through a medium with a different optical density, such as going from air to water or from one transparent material to another. It happens because the speed of light differs in different materials. When light travels from one medium to another at an angle, the change in speed causes the light rays to bend, or change direction. This bending of light is what we refer to as refraction.
To understand why refraction occurs, we can look at the principle known as Snell's Law. It states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to a constant value, known as the refractive index of the two media. This formula can be expressed as:
n₁sinθ₁ = n₂sinθ₂
Where:
- n₁ is the refractive index of the first medium
- n₂ is the refractive index of the second medium
- θ₁ is the angle of incidence
- θ₂ is the angle of refraction
From this equation, we can see that when light passes from a medium with a lower refractive index to a medium with a higher refractive index, the angle of refraction becomes smaller, causing the light to bend towards the normal line (a line perpendicular to the surface of the interface between the two media). Conversely, when light passes from a medium with a higher refractive index to a medium with a lower refractive index, the angle of refraction becomes larger, causing the light to bend away from the normal line.
Thus, refraction occurs due to the change in speed and direction of light as it travels from one medium to another, based on the principle of Snell's Law.