• Recognize situations where refraction will
• Identify which direction light will bend
when it passes from one medium to
• In this presentation we will discuss the
refraction of light and the situations in
which it occurs and why it happens.
• We will also discuss how refraction travels
through different mediums and how the
Discovery of Refraction
• Willebrord van Roijen Snell discovered
refraction in the early 1600’s.
• However refraction only became known
everywhere when Christian Huygens
published Snell’s and his own results in
“Dioptrica” and got the information out.
What is Refraction?
• When light passes from one medium into
a second medium, the light path bends.
• If a substance causes the light to speed
up or slow down more, it will refract more.
Why Does Refraction Occur?
• Refraction occurs when it is at the
boundary of a medium and it caused by
the change in speed.
• Light refracts because it travels at an
angle into a substance with a different
• FST= Fast to Slow, Towards the normal
• FSA= Slow to Fast, Away from the normal
What is the Refractive Index?
• It’s the ratio of velocity of light in two
media and hence it is a number without a
• The ratio of the speed of light in a vacuum
to the speed of light in a medium is called
the refractive index of the medium
Angle of Incidence
• The angle which the incident ray makes
with the normal ray at the point of
• The angle of incidence is basicly the
angle between the incident ray and the
Angle of Refraction
Its the angle that the refracted ray makes
with the normal line
What is a Lens?
• It’s a part of a transparent refracting
medium bounded by two spherical
surfaces or one curved and one plane
Two types: Biconvex and biconcave.
• It’s thicker at the middle than it is at the
• Parallel rays of light can be focused into a
This is the kind of lens used for a
• Is thinner at the middle than it is at the
• Light rays refract outwards and spread
apart as they enter the lens and again as
Henderson, Tom. "The Cause of Refraction." The
Cause of Refraction. Tom Henederson, 2013. Web. 25
Serway, Raymond A., and Jerry S. Faughn. "Refraction
." Holt physics. Austin, Tex.: Holt, Rinehart and
Winston, 2002. 487-492. Print.
Zobel, Edward . "Ray Optics, Light Refraction." Light
Refraction. N.p., n.d. Web. 25 Oct. 2013.