This document discusses interference of light waves. It explains that Thomas Young first described the properties of light interference using a double slit experiment. The experiment showed that light behaves as waves by producing bright and dark interference fringes on a screen. Constructive interference occurs when crest meets crest or trough meets trough, creating brighter areas. Destructive interference happens when crest meets trough, producing darker fringes. For an interference pattern to be stable, the light waves must have a single wavelength and maintain a constant phase relationship.

1. Interference of Light
By: Michael Alston
Joseph Chandler
&
Brandon Ray

3. Objectives
In this presentation, you will learn:
How light waves create bright and dark
fringes.
•
•
Requirements for interference to occur.

5. Introduction
● Light has properties similar to sound waves.
•
Its wave properties will help you understand
its interaction with objects close to its own
wavelength.

7. Interference of Light Waves
•
Occurs when two or more waves meet.
•
In Constructive Interference:
o The waves can either match crest-crest or
trough-trough and add together to make a
bigger wave.

8. Interference of Light Waves (con’t)
•
In Destructive Interference:
o The waves will phase and the crest of one will
meet the trough of the other and will cancel
each other out partially or completely.

10. Thomas Young
(1773-1829)
•
Thomas Young
was the first to
describe properties
and interference of
light.

11. Thomas Young (con’t)
● Light, because of its wave properties, will
have constructive and destructive
interference.
•
He sent sunlight through two narrow slits
and recorded an interference pattern on a
screen behind the two slits.

13. Double Slit Experiment
•
•
The double slit experiment shows how light
waves interfere with each other
There is a pattern of bright and dark fringes
on the screen

14. Double Slit Experiment (con’t)
•
The bright fringes
are areas where
the light travels the
same distance to
the screen and
creates
constructive
interference.

15. Double Slit Experiment (con’t)
•
The dark fringes are areas where the crest
of one wave matches up with the trough of
the other thus creating destructive
interference.

17. Requirements For Interference
•
In order for an interference pattern to be
stable the waves must…
o be emitted from a single consistent wavelength
or frequency.
o must maintain a constant phase relationship
with each other.

19. Evaluation Questions
1. The double slit experiment was first
conducted by __________.
2. Bright fringes are formed when
____________ interference occurs.
3. Dark fringes occurs when the crest of one
wave matches with the _________ of another
wave.

20. Evaluation Questions
4. What does the Double Slit Experiment
show?
5. How does Constructive Interference occur?
6. How does Destructive Interference occur?
7. What is one requirement for Interference?

21. Evaluation Questions
8. What does it mean to have a constant
phase relationship?
9. Light has properties similar to
_______waves.
10. In order for an interference pattern to be
stable, light must be emitted from a
______________.

23. Bibliography
·Interference. (n.d.). Interference. Retrieved October
29, 2013, from
http://physics.bu.edu/~duffy/py106/Interference.html
·Molecular Expressions Microscopy Primer: Physics of Light
and Color - Light: Particle or a Wave?. (n.d.). Molecular
Expressions Microscopy Primer: Physics of Light and Color Light: Particle or a Wave?. Retrieved October 29, 2013, from
http://micro.magnet.fsu.edu/primer/lightandcolor/particleorwav
ehome.html
·Two-Slit Experiments. (n.d.). Two-Slit Experiments. Retrieved
October 29, 2013, from
http://abyss.uoregon.edu/~js/21st_century_science/lectures/le
c13.html