When light travels from one medium to another, such as from air to water, the angle at which it approaches the interface between the two mediums is called the angle of incidence. Similarly, the angle at which light bends or changes direction upon crossing the interface is called the angle of refraction.
The specific angles of incidence and refraction are determined by Snell's law, which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the velocities of light in the two mediums. Mathematically, Snell's law can be expressed as follows:
n₁ * sin(θ₁) = n₂ * sin(θ₂)
where:
- n₁ is the refractive index of the initial medium (air in this case)
- θ₁ is the angle of incidence
- n₂ is the refractive index of the second medium (water in this case)
- θ₂ is the angle of refraction
For the case of light traveling from air to water, the refractive index of air is approximately 1, and the refractive index of water is around 1.33. Using Snell's law, we can derive the angles of incidence and refraction.
Typically, when light passes from air to water, the angle of incidence is larger than the angle of refraction. This means that the light bends towards the normal, an imaginary line perpendicular to the surface of the water. In other words, the light ray is refracted towards the normal as it enters the denser medium (water) from the less dense medium (air).
The exact values of the angles of incidence and refraction depend on the specific values of the angles and the refractive indices of the media involved. However, as a general observation, the angle of incidence is greater than the angle of refraction when light passes from air to water, and this bending of light is due to the change in its speed as it crosses the interface between the two media with different refractive indices.