Topic Cluster

Waves & Optics

Waves and optics: oscillations, sound and light as waves — wave speed, frequency and wavelength, interference, reflection and refraction, and how waves carry energy.

Waves and Optics — the core equations of waves and optics, and every article on the topic
The equations this topic keeps coming back to.

What Are Waves and Optics?

Waves and Optics are oscillations that travel: sound and light, and what happens when a wave meets a boundary, a slit or a lens. The same mathematics describes a guitar string and a radio mast.

Core equations in waves and optics
RelationshipEquationWhat it tells you
Wave speedv = f·λSpeed from frequency and wavelength
PeriodT = 1 / fTime for one full oscillation
Refractive indexn = c / vHow much a medium slows light
Snell's lawn1·sinθ1 = n2·sinθ2Refraction at a boundary
Thin lens equation1/f = 1/do + 1/diObject and image distance for a lens
Malus's lawI = I0 · cos²θIntensity through a polarizer
Infrared Radiation: Uses & Properties
Waves & Optics

Infrared Radiation: Uses & Properties

Infrared radiation is the 700 nm to 1 mm slice of the electromagnetic spectrum, just beyond the red end of what the eye can see, and one band name stretched over a factor of 1428.57 in wavelength. This page gives the range and the one relation that governs it, the five published ways of subdividing the band and why they disagree, what sits in each part from remote controls to far-infrared astronomy, why an infrared photon is weak compared with room temperature, and where the simple picture breaks down. Seven worked problems, two original diagrams, an interactive lab and a calculator.

21 min read
Ultraviolet Radiation: Types & Effects
Waves & Optics

Ultraviolet Radiation: Types & Effects

Ultraviolet radiation is the 100 to 400 nm region of the electromagnetic spectrum, split by convention into UVA, UVB and UVC. This page gives the three band boundaries and where they come from, the energy every ultraviolet photon carries in eV, joules and kJ/mol, which bands the atmosphere lets through and why, and the work-function threshold that explains why ultraviolet damages what visible light leaves alone. Seven worked problems, two original diagrams, an interactive lab and a calculator.

19 min read