The Electromagnetic Spectrum Cheat Sheet

Key Facts

• All electromagnetic waves travel through a vacuum at $c = 3.00 \times 10^8\ \text{m/s}$.
• Wave speed is related to wavelength and frequency by $c = \lambda f$ for electromagnetic waves in a vacuum.
• Frequency can be found using $f = \frac{c}{\lambda}$, where $f$ is in hertz and $\lambda$ is in meters.
• Wavelength can be found using $\lambda = \frac{c}{f}$, where $c$ is the speed of light.
• Photon energy is calculated with $E = hf$, where $h = 6.626 \times 10^{-34}\ \text{J}\cdot\text{s}$.
• Higher frequency means higher photon energy because $E$ is directly proportional to $f$.
• The electromagnetic spectrum from lowest to highest frequency is radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma ray.
• Visible light ranges approximately from $400\ \text{nm}$ violet light to $700\ \text{nm}$ red light.

Vocabulary

Electromagnetic wave

A transverse wave made of changing electric and magnetic fields that can travel through empty space.

Wavelength

The distance between matching points on a wave, such as crest to crest, represented by $\lambda$.

Frequency

The number of wave cycles passing a point each second, measured in hertz, or $\text{Hz}$.

Photon

A particle-like packet of electromagnetic energy with energy $E = hf$.

Ionizing radiation

High-energy radiation that can remove electrons from atoms, such as many ultraviolet rays, X-rays, and gamma rays.

Visible spectrum

The small part of the electromagnetic spectrum that human eyes can detect, roughly $400\ \text{nm}$ to $700\ \text{nm}$.