Diffraction is the bending of light around obstacles. Light diffracts through small openings more noticeably than larger openings, producing interference patterns of bright and dark fringes. A double slit experiment demonstrates diffraction through two slits, with light and dark fringes appearing from constructive and destructive interference. Diffraction gratings split light into multiple beams like how light spreads on a CD. Diffraction is used in microscopes and telescopes to resolve images by separating blurred images into distinct ones.

1. Diffraction of Light
By: Ryan Newman and Stella Oliver

2. Introduction of Diffraction
● In today’s lesson we’ll be talking about the
diffraction of light and how light bends
around objects.
•
We will also discuss how diffraction
determines an object’s ability to resolve
images.

3. Objectives
•
•
Describe how light waves bend around
obstacles and produce bright and dark
fringes.
Describe how diffraction determines an
optical instrument’s ability to resolve images.

4. What is diffraction?
•
Diffraction: the bending of light around an
obstacle
Think about...
Flashlight beams
Spotlights
Light shining out from a classroom
•
•
•

5. This picture
demonstrates how
light diffracts
through a tiny
opening.

6. Diffraction Openings
The size of the
opening determines
the extent to which the
light diffracts.
● Larger opening- less
noticeable diffraction
● Smaller openingmore noticeable
diffraction

7. Double Slit Diffraction
•
Produces diffraction patterns composed of dark
and light fringes
o Fringes: one of the various light or dark bands
•
http://www.colorado.edu/physics/2000/schroe
dinger/two-slit2.html
The diffraction from the two slits interfere with
each other.
o
o
Light fringes- areas of constructive interference
Dark fringes- areas of complete destructive interference

8. Diffraction Grating
● Diffraction Grating- an optical component
that has several closely spaced parallel
grooves that split and diffract light into
several beams
Diffraction grating can be
illustrated by how light
beams spread out on a
CD

9. Resolving Power of Diffraction
•
•
Diffraction is used in telescopes and
microscopes to resolve (clear up) images
Diffraction separates the blurred image into
different individual images

10. REVIEW QUESTIONS
1. Which of the following is NOT an example of diffraction?
a.
Taking a panoramic picture
b.
Light spreading through the hallway from an open
classroom door
c.
A projector bulb filling an entire SMART board
d.
A spotlight shining on a dancer
2. True or False: Dark fringes represent areas of constructive interference in
double slit diffraction.
3. When light diffracts through a small opening, how does it compare to the
diffraction of light through a wider opening?
4. Where is the brightest fringe located in a double slit diffraction illustration?
5. How does diffraction resolve microscopic and telescopic images?

11. Bibliography
Davidson, M. W. (n.d.). Molecular Expressions Microscopy Primer: Light and Color - Diffraction of
Light. Molecular Expressions Microscopy Primer: Light and Color - Diffraction of Light. Retrieved
October 28, 2013, from http://micro.magnet.fsu.edu/primer/lightandcolor/diffractionintro.html
Abramowitz, M., & Davidson, M. W. (n.d.). Diffraction of Light. Olympus Microscopy Resource
Center. Retrieved October 28, 2013, from
http://www.olympusmicro.com/primer/lightandcolor/diffraction.html
Hewitt, P. (2009). Conceptual Physics. New Jersey: Addison-Wesley and Pearson.
Classic Two-Slit Experiment. (n.d.). Classic Two-Slit Experiment. Retrieved October 23, 2013, from
http://www.colorado.edu/physics/2000/schroedinger/two-slit2.html
Diffraction Grating. (n.d.). Diffraction Grating. Retrieved October 24, 2013, from
http://www.physics.smu.edu/~scalise/emmanual/diffraction/lab.html