[Under Construction]

 

 

Radiant Energy:

Objectives:

    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:

 

Notes:

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:

Amplitude

         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)

Wavelength

        The distance between 2 consecutive crests or troughs  

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

(imagers.gsfc.nasa.gov)

Frequency

        The number of cycles per unit time

        Transverse crests(troughs)/second

        Compression compressions(rarefactions)/second

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

(www.lbl.gov/images)

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

 

(www.yorku.ca)

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