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
Relationship	Equation	What it tells you
Wave speed	v = f·λ	Speed from frequency and wavelength
Period	T = 1 / f	Time for one full oscillation
Refractive index	n = c / v	How much a medium slows light
Snell's law	n1·sinθ1 = n2·sinθ2	Refraction at a boundary
Thin lens equation	1/f = 1/do + 1/di	Object and image distance for a lens
Malus's law	I = I0 · cos²θ	Intensity through a polarizer

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Waves & Optics

What Is Amplitude in Physics?

Amplitude is the maximum displacement of a particle from its rest position as a wave passes through it. This guide covers the formula, the SI unit, how to read amplitude off a graph, seven worked problems, and why doubling amplitude quadruples the energy.

14 min read

Waves & Optics

The Speed of Sound (and What Changes It)

The speed of sound is about 343 m/s in dry air at 20 degrees Celsius. Temperature, the gas itself and humidity all shift it - but air pressure does not.

13 min read

Waves & Optics

Sound Waves: How They Travel

Sound waves are longitudinal pressure waves that travel by squeezing and stretching a medium. Learn the v = fλ formula, the speed of sound in air, water and steel, five real examples and seven worked problems.

15 min read

Waves & Optics

Wavelength: Definition, Formula and Units

Wavelength is the distance between two matching points on a wave, such as crest to crest. This guide covers the λ = v/f formula, SI units, five real-world examples and eight worked problems.

14 min read

Waves & Optics

Wave Speed in Different Media: Sound, Light and Strings

Wave speed is set by the medium, not the source: sound travels at 343 m/s in air but about 5,960 m/s in steel, while light slows from 299,792,458 m/s in a vacuum to roughly 124 million m/s in diamond. A full reference table, three formulas and eight worked problems.

15 min read

Waves & Optics

The Decibel Formula: Sound Intensity and Sound Level

The decibel formula, L = 10 log10(I/I0), turns sound intensity into a sound level in decibels. This guide covers the reference intensity, the +3 dB and +10 dB rules, a full chart of everyday sound levels and seven worked problems.

13 min read

Waves & Optics

Lens Equation (1/f = 1/do + 1/di)

The lens equation, 1/f = 1/do + 1/di, locates the image formed by any thin lens or spherical mirror. This guide covers the three sign rules, both textbook conventions, an interactive simulator and seven worked problems.

16 min read

$Refractive Index (n = c/v): Formula & Table$

Waves & Optics

Refractive Index (n = c/v): Formula & Table

The refractive index n = c/v tells you how much a material slows light. Get the full table of 15 values from air to diamond, plus worked examples and an interactive lab.

14 min read

Waves & Optics

What Is Polarization of Light?

Polarization of light is the direction a light wave's electric field vibrates in. Learn Malus's law (I = I0cos²θ), Brewster's angle, real-world examples and worked problems.

14 min read

$What Is Diffraction in Physics?$

Waves & Optics

What Is Diffraction in Physics?

Diffraction is the bending and spreading of waves through gaps and around edges. Learn the grating formula d sin θ = nλ with six real-world examples, worked problems and an interactive lab.

15 min read

Waves & Optics

Dispersion of Light and Prisms

Dispersion of light is why a glass prism splits white light into a rainbow. Learn why violet bends more than red, the key formulas, and 7 real-world examples.

15 min read

Waves & Optics

Concave vs Convex Mirror

A concave mirror curves inward and converges light to a real focus; a convex mirror bulges outward and diverges it from a virtual focus behind the glass. Ray diagrams, the mirror formula, seven worked problems and the reason your wing mirror lies about distance.

17 min read

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