# Introduction to Snell’s Law

Snell’s law, also known as the law of refraction, is a fundamental principle in optics that describes the behavior of light as it passes through different mediums. This law states that the ratio of the sines of the angles of incidence and refraction is equal to the ratio of the refractive indices of the two mediums. In simpler terms, this means that the angle at which light enters a medium affects the angle at which it exits, depending on the refractive index of the medium.

The law is named after Dutch mathematician Willebrord Snell, who first described it in 1621. Snell’s law is a crucial concept in the study of optics, as it explains phenomena such as why objects appear distorted when viewed through water or a curved lens. It is also used to calculate the angle of refraction when light passes through different mediums.

# Understanding and Applying Snell’s Law

To apply Snell’s law, one must first understand the concept of refractive index. Refractive index is a measure of how much light is bent or refracted when passing through a medium, compared to its speed in a vacuum. Each medium has its own refractive index, which is determined by its density and other properties.

When light passes from one medium to another, such as from air to water, it changes speed and direction. The angle at which the light enters the medium is called the angle of incidence, while the angle at which it exits is called the angle of refraction. By using Snell’s law, one can calculate the angle of refraction based on the refractive indices of the two mediums and the angle of incidence.

# Common Snell’s Law Problems

Some of the most common problems involving Snell’s law include finding the angle of refraction when light passes through different mediums at different angles, calculating the refractive index of a medium based on the angle of incidence and refraction, and determining the critical angle at which light is totally reflected rather than refracted. These problems require an understanding of the principles of Snell’s law and the ability to apply mathematical formulas to calculate the answers.

# Examples and Solutions to Snell’s Law Problems

Example 1: A ray of light enters a glass medium at an angle of 30 degrees. If the refractive index of glass is 1.5, what is the angle of refraction?

Solution: Using Snell’s law, we can calculate the angle of refraction using the formula n₁sinθ₁ = n₂sinθ₂, where n₁ and θ₁ are the refractive index and angle of incidence, respectively, and n₂ and θ₂ are the refractive index and angle of refraction. Plugging in the values, we get sin(30) / 1.5 = sin(θ₂), which gives us an angle of refraction of 19.47 degrees.

Example 2: A ray of light enters a diamond medium at an angle of 42 degrees. If the angle of refraction is 23 degrees, what is the refractive index of diamond?

Solution: Rearranging the formula from above, we get n₂ = (n₁sinθ₁) / sinθ₂. Plugging in the values we have, we get n₂ = (1sin(42)) / sin(23), which gives us a refractive index of 2.41.

Example 3: What is the critical angle for a beam of light passing from water (refractive index 1.33) to air?

Solution: The critical angle is the angle at which light is totally reflected rather than refracted. To calculate this angle, we use the formula sin(critical angle) = n₂ / n₁, where n₁ is the refractive index of the first medium (water) and n₂ is the refractive index of the second medium (air). Plugging in the values, we get sin(critical angle) = 1 / 1.33, which gives us a critical angle of 48.75 degrees.