This presentation introduces the characteristics of light and the electromagnetic spectrum. It discusses the different types of electromagnetic waves including their frequencies and wavelengths. It describes the parts of a wave like amplitude, frequency, period, and wavelength. It explains that light travels at a finite speed of 299,792,458 meters per second. It also covers how the brightness of light decreases with the inverse square of the distance from the source.

1. Characteristics
of Light
Emily Tripp and Stephen Byrd

2. Objectives
•
After this presentation, students will be able
to:
o
identify the components of the electromagnetic
spectrum and explain the different types of radiation.
o
calculate the frequency and wavelength of an
electromagnetic wave, and label the different parts of
a wave.

3. Objectives
•
After this presentation, students will be able
to:
o
Realize that light has a finite speed that does not
move any faster or slower.
o
Describe how brightness is affected by distance, and
give real-life examples.

4. Introduction: Characteristics of
Light
• In this presentation, you will be learning about the
electromagnetic spectrum, specifically visible light and the
different wavelengths and frequencies of different
components of the EM spectrum.
•
•
•
We will be reviewing the different parts of a wave and how to
calculate frequency and wavelength.
We will also talk about the fact that light has a finite speed
that does not change.
We will demonstrate how the brightness of light is affected by
distance and also explain why this happens.

5. The Electromagnetic Spectrum
•
•
•
The electromagnetic spectrum is made up of
many different types of electromagnetic waves.
Radio waves, microwaves, infrared
waves, visible light, UV light, X rays, and
gamma rays make up the EM spectrum.
For each type of these electromagnetic
waves, frequency and wavelength are different.

6. The Electromagnetic Spectrum

7. Height
Review: Parts of a Wave

8. Frequency
•
•
•
The period of a wave is the time it takes to
complete a cycle of motion.
The frequency of an electromagnetic wave is the
number of cycles that occur in a given amount of
time. This unit is expressed as Hertz (Hz).
Frequency and period are inverse; frequency is
equal to 1/period, and the period is equal to
1/frequency.

9. Wavelength
•
•
The wavelength of an electromagnetic wave
is the length from any point on a wave to the
same point on the next wave. The
wavelength of a wave is usually given.
This is an example of one wavelength.

10. Speed of Light
•
•
•
•
Light has a finite speed: this means that it never changes. It
has a definite speed that can never change on it’s own.
This speed is rounded as 3.0 x 108 meters per second, but
the actual number is 299 792 458 meters per second.
A beam of light could travel around the earth 7.5 times in
one second.
The distance that light travels in one year is called a light
year.

11. Brightness vs. Distance
•
•
•
•
When the distance from a light source doubles, its
brightness decreases by a factor of four. This is called
the inverse square law.
The most common example is the light from a star to
the earth.
The brightness depends on the distance and how much
light the source produces: “luminosity”.
Luminous flux is the rate at which light is emitted from a
source, and this is measured in lumens.

12. Questions
1. Can you name at least 5 of the 7 types of waves in the
electromagnetic spectrum?
1. What is the amplitude of a wave?
1. What is a period? How do you calculate it?
1. How do you calculate frequency?
1. What is wavelength?

13. Questions
6. What is the speed of light?
7. Can the speed of light get faster or slower? Why or why
not?
8. What is the inverse square law?
9. What is luminosity?
10. What did you learn from our demonstration?

14. Bibliography
Serway, R. A., & Faughn, J. S. (2009). Physics. Austin: Holt.
Hewitt, P. G., & Chiaverina, C. (2009). Light. Conceptual physics: the high
school physics program (pp. 532-546). Boston, Mass.: Pearson/Prentice
Hall.
Mattson, B., & Gibb, M. (n.d.). Electromagnetic Spectrum - Introduction.
Imagine The Universe! Home Page. Retrieved October 22, 2013, from
http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
Foster, A. (2006, October 18). Education.com | An Education & Child
Development Site for Parents | Parenting & Educational Resource.
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