Final answer:
Snell's law relates the indices of refraction and the angles of incidence and refraction when light passes through different media. It is expressed as n1 sin θ1 = n2 sin θ2. By knowing the indices of refraction and the incident angle, one can calculate the refracted angle.
Step-by-step explanation:
Snell's law, also known as the law of refraction, is a fundamental principle in physics that describes the behavior of light as it travels through different media. The law states that the product of the index of refraction of the first medium and the sine of the incident angle is equal to the product of the index of refraction of the second medium and the sine of the refracted angle. It is mathematically expressed as n1 sin θ1 = n2 sin θ2, where n1 and n2 are the indices of refraction of the first and second media, and θ1 and θ2 are the angles exactly measured from the normal (perpendicular) to the interface. Snell's law is applicable for any wavefront passing from one medium to another, including light and sound, as long as the media have different propagation speeds.
By applying Huygens's principle we can understand the change in wavefront direction when it crosses the interface between two media with different speeds of light. Each point of the wavefront acts as a source of secondary wavelets, the envelope of which becomes the new wavefront. This process explains why a wavefront changes direction when it passes from one medium to another with a different speed, typically bending towards the normal when it enters a medium where it travels slower.
By knowing the index of refraction for each media and the incident angle, one can use Snell's law to calculate the angle of refraction, which is key for understanding phenomena like total internal reflection and the behavior of lenses. Recall that when the incident angle reaches the critical angle, the refracted angle is 90°, indicating that the light ray travels along the boundary of the two media, beyond which it reflects entirely back into the original medium.