The Electromagnetic Spectrum

The Electromagnetic Spectrum:

• Electromagnetic waves are electric and magnetic disturbances that transfer energy from one place to another.

Gamma rays

X-rays

Ultraviolet

Visible Light

Infra-red

Microwaves

Radio Waves

Wavelength:

• The wavelength is the distance form one wave peak to the next wave peak along the waves
• Radio waves have the longest wavelengths of more than 1km.
• X-rays and gamma rays have the shortest wavelengths of less than a millionth of a millionth of a metre (= 0.000,000,000,001m)

Frequency:

• Frequency of an electromagnetic wave is the number of complete waves passing a point each second. 
• This is measured in Hertz (Hz), Kilohertz (kHz) and Megahertz (MHz) 
• I Hertz = 1 complete wave per second 
• Gamma rays have the highest frequency  
• Radio waves have the lowest frequency 

The speed of electromagnetic wave:

• All electromagnetic wave travel at the speed of light (300million m/s) through space or a vacuum.
• We can work out the wave speed using frequency and wavelength:

               Wave speed    =    Frequency    X   wavelength

                   (m/s)                     (Hz)                     (m)

Other equations:

Frequency   =                 1

                      Time period of 1 wave

Time of 1 wave   =          1

                                  Frequency

Gamma Rays:

• It is electromagnetic radiation from radioactive substances.
• Gamma rays are used for:
  •  
    •  
      • Killing harmful bacteria in food
      • Sterilising surgical instruments
      • Killing cancer cell – they direct a narrow beam of gamma radiation at the cancerous cells. The beam is aimed at it from different directions on order to kill the tumour but not the surrounding tissue

·         Gamma rays can also be dangerous because they can cause cancer as well as killing it. Small doses of gamma radiation can cause cell mutation by damaging the DNA. High doses can kill living cells.

X-rays:

• X-rays pass through soft tissue but are absorbed by bones…