Electromagnetic
Radiation
Wave
Do The Wave
Groups 3-5
List types of waves (and how they are
used)
7 minutes
Wavelength (l) – distance between two consecutive
peaks of a wave
Frequency (Hz or s-1) – number of waves passing
through a given point per second
c = ln
Far infrared waves are thermal. In other
words, we experience this type of infrared
radiation it every day in the form of heat!
Shorter infrared waves are not hot at all - in
fact you cannot even feel them. (TV remote
control).
Translated into visible light so we can see it
WAVES
http://www.colorado.edu/physics/2000/s
chroedinger/small_interference.html
http://www.colorado.edu/physics/2000/s
chroedinger/two-slit2.html
Waves
Insect in water
Pit Viper
Difference between waves of water and
waves of light?
Light moves at c=3.00x108 m/s
Light is a particle and a wave
Light is 3 Dimensional
Energy
What do we mean light is also a particle?
Light does not have mass, but is made of
photons
Photons have fixed, discrete energy levels
E=hv

h = Planck’s constant = 6.626 x 10-34Js
The intensity of visible light can be increased or
decreased only by changing the number of
photons present (photoelectric effect)
http://www.colorado.edu/physics/2000/schroedinger/two-slit3.html
http://web.mit.edu/8.02t/www/802TEAL3
D/visualizations/light/EBlight/EB_Light.
mpg
Wavelength (l) – distance between two consecutive
peaks of a wave
Frequency (Hz or s-1) – number of waves passing
through a given point per second (v)
c = ln

c=3.00x108 m/s
E=hv

h = Planck’s constant = 6.626 x 10-34Js
Sample Problems
1. Calculate the energy of EMR that has a
frequency of 2.8 x 109 Hz.
2. Calculate the frequency of a wave that has
a wavelength of 1.0 x 10-4m. What type of
EMR is it?
3. What is the speed of EMR with a
frequency of 5.32 x 105Hz?
4. What is the energy of visible light with a
wavelength of 500.nm? What color is the
light? (1m = 1 x 109nm)
Sample Answers
1. E = hn

E = (6.626x10-34Js)(2.8x109s-1) = 1.9x10-24J
2. c = ln


(3.00 x 108m/s) = (1.0x10-4m)n
n = 3.0 x 1012s-1;
3. 3.00 x 108m/s (speed of all EMR)
4. E = hn





c = ln
n = c/l
E = h(c/l)
E = (6.626 x 10-34Js 3.00 x 108m/s)
E = 3.98 x 10-19J (Green)
(5.00 x 10-7m)
Homework
Read p. 275-278
P. 321 #31, 34, 35