In geometric optics, light is treated as rays that travel in straight lines. These rays can be reflected, refracted, or absorbed by different materials, and their behavior can be described using principles such as Snell's law and the law of reflection.
The law of reflection states that the angle of incidence is equal to the angle of reflection. This can be proven using basic geometry and the fact that light rays travel in straight lines. When a ray of light hits a smooth, flat surface, it will bounce off at the same angle it hit the surface, creating a reflection.
Snell's law describes the relationship between the angles of incidence and refraction when light passes through a boundary between two materials. It can be derived using the principle of Fermat's principle, which states that light will always follow the path that takes the shortest amount of time. Through mathematical calculations, this principle leads to the equation n₁sinθ₁ = n₂sinθ₂, where n₁ and n₂ are the refractive indices of the two materials and θ₁ and θ₂ are the angles of incidence and refraction, respectively.
In some cases, the behavior of light can be accurately described using only geometric optics. This is true for simple, homogeneous materials and situations where the size of the objects involved is much larger than the wavelength of the light. However, in more complex situations, such as when light interacts with microscopic structures or when it passes through multiple materials with varying refractive indices, other branches of optics, such as wave optics, must be considered.
In geometric optics, the speed of light is assumed to be constant and is not explicitly considered in calculations. This is because geometric optics treats light as rays that travel in straight lines, rather than waves. However, the speed of light is still an important fundamental constant that plays a role in many optical phenomena, and it is typically used to convert between different units of measurement when working with geometric optics.