The Wave Nature of

Light

Section 6.1

ObjectivesStudy light (radiant energy or electromagnetic radiation) as having wavelike properties.

Identify the characteristics of wavelength, frequency, and speed

Key TermsElectromagnetic radiation

Wavelength

Frequency

Speed

Why Study Light?Our understanding of the electronic structure of atoms came from the analysis of light either emitted or absorbed

Visible Light

Light we can see with our eyes

An example of electromagnetic radiation

Electromagnetic Radiation

Carries energy through spacea.k.a radiant energy

Many types of ERVisible lightRadio wavesInfrared radiationX rays

The different forms of ER share certain fundamental characteristics

They all move through a vacuum as the speed of light:

3.00 x 108 m/s

Radio AND X rays??

Wavelike Characteristics

All ER types also behave like water waves

Up and down motion

Pattern of peaks and troughs repeated at regular intervals

Wavelength, Shortest distance between equivalent points on a continuous wave

Between 2 adjacent peaks or troughs

Measure in meters or nm

Frequency, Number of complete wavelengths or cycles that pass a given point per second.

Measured in Hz (Hertz)

AmplitudeWave’s height from the origin to a peak, or from the origin to a trough

Relates to the intensity of the radiation

Characteristics of Waves

What makes water waves travel at various speeds?

ER versus Water Waves

ER move at the same speed

Wavelength and frequency are always related

c

c

c

Why Your Radio Won’t Take an X rayER types have different properties as a result of their varying wavelengths, expressed in units of length

Electromagnetic Spectrum

A VERY Large Spectrum

Gamma rays =

Radio waves =

Don’t Forget…

ROY G BIV

Order of colors (LS) on the visible spectrum

Practice Problem• The yellow light given off by a sodium

vapor lamp used for public lighting has a wavelength of 589 nm. What is the frequency of this radiation?

Solution