Download The Refraction of Light

The Refraction of
Light
SNC2P – Optics
Refraction
Refraction: the bending or change in direction of light when it
travels from one medium into another
• Refraction occurs because light travels at different speeds
through different media
Rules for Refraction
The Rules for Refraction
1. The incident ray, the refracted ray and the normal all lie in
the same plane. The incident ray and the reflected ray are
on opposite sides of the line that separates the two media.
2. Light bends toward the normal when the speed of light in
the second medium is less than the speed of light in the first
medium. Light bends away from the normal when the
speed of light in the second medium is greater.
Angle of Refraction: the angle between the refracted ray and
the normal.
Total Internal Reflection
Total Internal Reflection
• When light travels from one medium into another, some
of the light is reflected and some is refracted.
• Recall: Light bends away from the normal when it speeds up at
the boundary of two media (example: as light travels from water
to air)
• As angle of incidence increases, the angle of refraction increases
• The angle of incidence which results in the angle of refraction
becoming 90o is known as the critical angle
• If the angle of incidence increases past the critical angle the
refracted ray will no longer exit the medium. Instead, it will reflect
back into the medium. This is known as total internal reflection.
• Water has a critical angle of 48.8o
Total Internal Reflection and
the Critical Angle
• Diamonds have a high index of refraction which means
that they have a very small critical angle: 24.4o
• A light ray can bounce around several times inside the diamond
before eventually exiting through a top face of the gemstone
• This causes the “sparkling” effect
• Fibre optics is a technology that uses light to transmit
information along a glass cable
• Information is transferred into light energy and enters one end of
the optical fibre. Due to the small critical angle, internal
reflection occurs along the length of the optical fibre until the
light emerges at the end and is then decoded
Demo and Video
Refraction
Homework
• Complete the worksheet and the questions on the handout.