Understanding the Law of Refraction

The question asks to identify the physical law that states the ratio between the sine of the angle of incidence and the sine of the angle of refraction is a constant value. This phenomenon describes how light bends when it passes from one transparent medium to another.

Snell's Law Explained

Snell's law accurately describes this relationship. It quantizes the bending of light (refraction) as it crosses the boundary between two different isotropic media, such as air and water, or glass and air.

Mathematically, Snell's law is expressed as:

$$ \frac{\sin(\theta_1)}{\sin(\theta_2)} = \frac{v_1}{v_2} = \frac{n_2}{n_1} = \text{constant} $$

Where:

• $\theta_1$ is the angle of incidence (the angle between the incoming ray and the normal to the surface).
• $\theta_2$ is the angle of refraction (the angle between the refracted ray and the normal to the surface).
• $v_1$ and $v_2$ are the speeds of light in the first and second medium, respectively.
• $n_1$ and $n_2$ are the refractive indices of the first and second medium, respectively.

The law essentially states that for a given pair of media, the ratio of the sines of these angles is constant, and this constant is equal to the ratio of the speeds of light in the two media or the inverse ratio of their refractive indices.

Why Other Laws Don't Apply

• Gravitational law: This law, formulated by Isaac Newton, describes the gravitational force between two objects with mass. It does not relate to the behavior of light or angles of incidence and refraction.
• Reflection law: The laws of reflection state that the angle of incidence is equal to the angle of reflection ($\theta_i = \theta_r$), and that the incident ray, the reflected ray, and the normal all lie in the same plane. This deals with light bouncing off a surface, not passing through it.
• Gauss law: In electromagnetism, Gauss's law relates the electric field divergence to the electric charge density. It is fundamental to understanding electric fields but is unrelated to the refraction of light.

Therefore, the law that states the ratio of the sine of the angle of incidence and the sine of the angle of refraction is constant is Snell's law.