Electromagnetic Spectrum Properties and Order

The electromagnetic (EM) spectrum is a continuous range of transverse waves that all travel at the speed of light in a vacuum ($3.0 \times 10^8$ m/s). They are produced by vibrating charges and do not need a medium to travel.

The seven regions (in order of decreasing wavelength)

Region	Wavelength range	Frequency
Radio waves	> 0.1 m	Lowest
Microwaves	1 mm to 0.1 m
Infrared	700 nm to 1 mm
Visible light	400 nm to 700 nm
Ultraviolet	10 nm to 400 nm
X-rays	0.01 nm to 10 nm
Gamma rays	< 0.01 nm	Highest

Common properties of all EM waves

• Transverse waves.
• Travel at $3.0 \times 10^8$ m/s in a vacuum.
• Transfer energy.
• Can be reflected, refracted and diffracted.
• Do not need a medium (travel through a vacuum).
• Obey $v = f\lambda$.

Hazards of high-frequency EM radiation

Higher frequency means higher energy per photon. Ultraviolet, X-rays and gamma rays can damage living cells.

Region	Hazard
Ultraviolet	Sunburn, skin cancer, eye damage
X-rays	Cell damage, cancer with prolonged exposure
Gamma rays	Cell damage, radiation sickness, cancer

Common errors and how to correct them

Listing the spectrum in the wrong order. Remember the order by the mnemonic: Runny Mashed Invisible Vegetables Usually eXplode Grossly (Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma).

Saying different EM waves travel at different speeds. In a vacuum, all EM waves travel at the same speed. The speed only differs when they pass through a material (refraction).

How to apply this in an exam

Know the order from longest wavelength (radio) to shortest (gamma). For uses and hazards, give one specific example per region rather than a generic statement.