Refraction in Prisms & Lenses

What is Refraction?

Refraction is the bending of light as it passes from one medium to another. This happens because light travels at different speeds in different media.

For example:

• When light passes from air into glass, it slows down and bends towards the normal.
• When it exits the glass back into air, it speeds up and bends away from the normal.

Refraction in Prisms

A prism is a transparent optical element with flat, polished surfaces that refract light. The most common type is a triangular prism.

• Dispersion: Prisms can split white light into its constituent colors (spectrum) due to different angles of refraction for different wavelengths.
• Angle of Deviation: The angle between the incident ray and the emerging ray is called the angle of deviation.

Refraction in Lenses

Lenses are curved pieces of glass or other transparent materials that refract light to converge or diverge beams.

• Converging Lenses (Convex): These lenses are thicker in the middle and bring light rays together at a point called the focus.
• Diverging Lenses (Concave): These lenses are thinner in the middle and spread light rays apart.

Laws of Refraction

The laws of refraction are governed by Snell's Law, which states:

$$n_1 \sin \theta_1 = n_2 \sin \theta_2$$

• $n_1$ and $n_2$ are the refractive indices of the two media.
• $\theta_1$ is the angle of incidence, and $\theta_2$ is the angle of refraction.