The Electromagnetic Spectrum


    1.    Identify the parts of the electromagnetic spectrum.

    2.    Explain the relationship between wavelength and frequency.




Electromagnetic Spectrum:

        Waves are aligned according to their photon energy, f & l

        Consists of:

        Radio waves


        Visible light



        Gamma rays

Visible spectrum:

        The portion that you can see

        Made up of many different colors (red - violet)

        430 -760 trillion Hz

Invisible Spectrum:

        Frequency above 760 or below 430 trillion Hz

Radio waves - lowest f and highest l

        Used in TV and radio

        l range from 1mm - 30km

        Can be varied by changing amplitude or f

        The changing of f or amplitude is called modulation

AM radio:

        has long l (500,000 - 2mill. Hz)

        Many TV stations - sound

        Long l allows reception around obstacles

FM Stations:

        Modulate frequency

        87mill - 108mill Hz

        Color portion of TV

        Are blocked by large objects


        1 bill. - 1 trillion Hz

        used for communication or cooking

        Short-l are used in radar

        Radio detecting and ranging

Infrared (IR):

        Just below visible

        Can feel as heat

        Anything that gives off heat gives off IR

Ultraviolet (UV):

        Just above visible

        Photon energy is large enough to kill cells

        Used in hospitals to kill bacteria

        Causes skin to make Vit D - for bones

        Causes skin to burn


        High energy photons can pass through soft tissue

        Absorbed in bone and hard materials such as lead

        Over exposure is harmful

Gamma Rays

        Highest energy photons

        From outer space & certain radioactive materials

        Can penetrate up to 3m in concrete

        Used in medicine to treat cancer

        Exposure con cause severe illness