Snell's law

High School

Definition

A law that describes how light bends, or refracts, when it passes from one medium into another. It relates the angles of incidence and refraction to the refractive indices of the two media, explaining effects such as a straw appearing bent in water.

Worked examples

\(n_1 \sin(\theta_1) = n_2 \sin(\theta_2)\)

Snell's law equation: refractive indices and angles relate across the boundary between two media.

Light enters water (\(n = 1.33\)) from air (\(n = 1.00\)) at \(45^\circ\); it refracts to \(32^\circ\).

Light bends toward the normal when entering a denser medium because water has a higher refractive index.

Common mistakes

Using the angles measured from the boundary surface instead of the normal → Always measure \(\theta_1\) and \(\theta_2\) from the perpendicular normal line Angles in Snell's law are defined relative to the normal, not the surface itself.
\(n_1 \sin(\theta_1) = n_2 \sin(\theta_2)\) with subscripts 1 and 2 swapped between sides → Keep each medium's \(n\) with its own angle: \(n_1\) pairs with \(\theta_1\), \(n_2\) with \(\theta_2\) Subscripts must match: the incident medium's index multiplies the incident angle.
Thinking light always bends away from the normal when crossing boundaries → Light bends toward the normal entering denser media, away when entering less dense media The direction of bending depends on whether refractive index increases or decreases.

Where you'll use it next

You'll apply Snell's law when studying lenses, prisms, fiber optics, and total internal reflection in physics, and it underpins understanding optical instruments like microscopes and cameras.

Found in 1 StudyPug lesson

Refraction of Light and Snell's Law: Unraveling the Mysteries of Light Bending

Physics 11

Dive into the fascinating world of light refraction and Snell's Law. Understand how light bends, calculate angles, and apply your knowledge to real-world scenarios. Perfect for aspiring physicists and curious minds!

11th Grade11th