The Electromagnetic Spectrumhttp://www.youtube.com/watch?v=bjOGNVH3D4Y

Learning Outcomes• State Typical values for the wavelengths of different

regions of the electromagnetic spectrum.• State that all electromagnetic waves travel at the same

speed in a vacuum• Describe differences and similarities between different

regions of the electromagnetic spectrum• Describe some uses of different parts of the

electromagnetic spectrum.• Describe the characteristics and dangers of UV-a, UV-B

and UV-C radiation

Why Electromagnetic?

http://www.phys.hawaii.edu/~teb/java/ntnujava/emWave/emWave.html

What links them all?

• They can all travel through a vacuum• They all possess both an Electric and Magnetic

wave interlocked and at right angles to each other

• They all travel at the speed of light in free space (299 792 458 ms-1 ……3.0 x 108 ms-1)

• They are all transverse waves

So why are there so many different types?• Electromagnetic waves of different types have

different characteristic wavelengths and therefore frequencies.

• The range of wavelengths in the electromagnetic spectrum range from 10-16m to 104m

• What is the frequency range of the electromagnetic spectrum?

Different “regions” (ranges of wavelengths)

Gamma rays

• Wavelengths: 10-16 – 10-9 m• Frequency range: 3 x 10 24 – 3 x 1017 Hz• Produced by: Nuclear decay or nuclear

accelerator• Detected by: Photographic film, geiger tube• Uses: Diagnoses and cancer treatment

X-Rays

• Wavelengths: 10-12 – 10-7 m• Frequency range: 3 x 10 20 – 3 x 1015 Hz• Produced by: Bombarding metals with high-

energy electrons• Detected by: Photographic film, flourescence• Uses: CT scans, X-ray photography, grystal

structure analysis

Ultraviolet radiation

• Wavelengths: 10-9 – 3.7 x 10-7 m• Frequency range: 3 x 10 17 – 8.0 x 1014 Hz• Produced by: High temperature solids and gases• Detected by: Photographic film, phosphors,

sunburn• Uses: disco lights, tanning, counterfeit

detection, detergents.

Types of UV

• UV-A: Wavelength 315 – 400nm; causes tanning when skin is exposed to the Sun (99% of UV light)

• UV-B: Wavelength 280 – 315nm; causes damage such as sunburn and skin cancer

• UV-C: Wavelength 100 – 280nm; is filtered out by the atmosphere and does not reach the surface of the Earth.

Visible Light

• Wavelengths: 3.7 x 10-7 – 7.4 x 10-7 m• Frequency range: 8.0 x 10 14 – 4.0 x 1014 Hz• Produced by: high temperature solids and

gases, lasers• Detected by: Photographic film, retina of the

eye• Uses: Sight, communication

Infrared radiation

• Wavelengths: 7.4 x 10-7 – 10-3 m• Frequency range: 4.0 x 10 14 – 3 x 1011 Hz• Produced by: Oscillation of molecules, from all

objects at temperatures above absolute zero• Detected by: Photographic film, thermopile,

heating of skin• Uses:

Microwaves

• Wavelengths: 10-4 – 10-1 m• Frequency range: 3 x 1012 – 3 x 109 Hz• Produced by: magnetron, klystron oscillators,

using oscillators to set up oscillations in a cavity• Detected by: heating effect, electrical circuits• Uses: radar, mobile phones, microwave ovens,

satellites navigation

Radio waves

• Wavelengths: 10-1 – 104 m• Frequency range: 3 x 109 – 3 x 104 Hz• Produced by: electrons oscillated by electric

fields in aerials• Detected by: resonance in electronic circuits• Uses: television, radio, telecommunications

Think of one innovative use for a region of the electromagnetic spectrum to share with the class.