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Radiant Energy:


    1.    Describe a wave in terms of its frequency, speed, and amplitude.

    2.    Identify the major regions of the electromagnetic specrtum.

Key Terms:

    electromagnetic radiation    amplitude    wavelength    frequency    speed of light    visible spectrum

Web Resources:



Waves and Energy:  

Light travels in electromagnetic waves.  A wave is a disturbance that transfers energy through matter or space.    All waves can be characterized by the following four characteristics: amplitude, wavelength, frequency, and speed.

Characteristics of Waves:

All waves share certain characteristics:


         The maximum distance the molecules are displaced from their starting place

        As energy , amplitude  

(by Cattell and J. Dombeck (Univ of Minnesota) and M. Temerin and F. S. Mozer (Univ of Ca, Berkeley)


        The distance between 2 consecutive crests or troughs  

Diagram showing the top of a wave is a crest, the 
bottom is a trough.



        The number of cycles per unit time

        Transverse crests(troughs)/second

        Compression compressions(rarefactions)/second

        Unit is the hertz (Hz)                        1Hz = 1wave/second


Speed of Waves:

The speed of a wave is determined by the number of waves passing a point per second and the length of the wave.

        Speed in any given medium is constant.

        Speed = frequency wavelength (f l)

If f ,l or f , l

  Waves through a medium:

A medium is any substance or region through which a wave is transmitted.

        Solid, liquid, or gas

        Transfers energy only without any net movement

2 properties of a medium affect wave speed

        Density- density slows the wave

        Elasticity - elasticity speeds up a wave


Light Energy:

The atom is the source of all light.

When an atom absorbs electricity its electrons (e-) become excited
The excited e- jumps to higher energy orbits
As the excited e- looses energy, it falls back to its original orbit and releases a photon.
A photon is a tiny packet or bundle of energy that contains the exact amount of energy that the atom absorbed.

        The amount of energy a photon contains determines what type of light is emitted



Electromagnetic Waves: (Light)

        All forms of light travel at 3x108 m/s in a vacuum

        Light requires no medium

        All electromagnetic waves are transverse waves

        2 waves- Electric wave & Magnetic wave

        Waves are at 90o angles



Last modified: September 28, 2003