Name:

# Electromagnetic Spectrum Activity - Gamma rays

## Resources

• NASA EM Spectrum Information Pages Gamma rays • Discovery Education EM Spectrum • List of SI (metric) prefixes . e.g. nano, milli, mega, tera.

Gamma rays are the most energetic electromagnetic wave. Gamma rays are ionizing radiation. Ionizing radiation has enough energy to tear electrons away from their atoms. The atoms are now 'ions'. These ions can cause unwanted chemical reactions in a material or organism.

With shorter wavelengths it is more common to refer to the wave's wavelength rather than its frequency. Gamma rays have wavelengths less than 10 pm (pm = picometers = 1x10-12). The frequency would be expressed in Ehz (exahertz) . A high frequency wave has a short wavelength. The relationship is defined as:

• Variables:   λ=wavelength (m)     v = speed of light (3 x 108 m/s)     f = frequency (Hz). Note EHz = 1 x 1018
• Formula:   λ = v ÷ f
• Example:   λ = 3 x 108 m/s ÷ 30 EHz = 10pm

In nature, gamma rays are produced through radioactive decay and by charged particles moving in magnetic fields.

Gamma rays are used to sterilize medical instruments, preserve foods by killing decay causing bacteria, security scanning. The extreme energy these rays have limits their use around humans, except when that dangerous energy is used to kill cancer cells. Focused beams of gamma rays can be used to target specific locations with the 'gamma knife'.

## EM Spectrum Data Table

Name Wavelength Range Wavelength
(comparative size)
Frequency Range Energy
ionizing/ med / lo
Sources Uses
Gamma rays

## Waves Glossary

Electromagnetic waves
Radiation consisting of waves of energy sent through space and matter associated with electric and magnetic fields resulting from the acceleration of an electric charge (light, Gamma rays , microwaves, gamma rays, etc.). 3.9
Frequency
The number of back-and-forth cycles per second, in a wave or wave-like process. 3.5
Period
The time for one wavelength to pass a point. The time for a wave to travel the distance of one wavelength. P= 1/frequency. 3.5
Wave
A rhythmic disturbance that transfers energy from place to place. 3.5
Wavelength
The distance measured from crest to crest of one complete wave or cycle. 3.5