Total Internal Reflection (TIR)
Occurs when the angle of incidence is greater than the critical angle and
Refractive index is a ratio (has no units).
the incident material is more optically dense than the second material. Optical fibres are long, very thin strands
of glass that can be used to transmit
Less to more optically dense
information through TIR. They are used in
medium: towards normal (air
An image in a mirror is: endoscopes and communications.
to water). r<i
• Virtual => no light is actually where the image appears The larger the refractive index of a
• Laterally inverted material, the smaller the critical angle. More to less optically dense
• Same distance from the mirror as the real medium: away from normal
Snell’s Law:
(glass to air). r>i
Reflection occurs when a wave hits a boundary
between two media and does not pass through, Reflection, Refraction Refraction occurs when a wave passes a
but instead stays in the original medium. boundary between two different transparent
media and undergoes a change in direction.
Law of Refraction Ray Diagram
Reflection
Speed and
wavelength of the
wave changes,
frequency (therefore
colour) does not. If i = r, the angle of
refraction is 90º.
Occurs when the angle of incidence is greater than the critical angle and
Refractive index is a ratio (has no units).
the incident material is more optically dense than the second material. Optical fibres are long, very thin strands
of glass that can be used to transmit
Less to more optically dense
information through TIR. They are used in
medium: towards normal (air
An image in a mirror is: endoscopes and communications.
to water). r<i
• Virtual => no light is actually where the image appears The larger the refractive index of a
• Laterally inverted material, the smaller the critical angle. More to less optically dense
• Same distance from the mirror as the real medium: away from normal
Snell’s Law:
(glass to air). r>i
Reflection occurs when a wave hits a boundary
between two media and does not pass through, Reflection, Refraction Refraction occurs when a wave passes a
but instead stays in the original medium. boundary between two different transparent
media and undergoes a change in direction.
Law of Refraction Ray Diagram
Reflection
Speed and
wavelength of the
wave changes,
frequency (therefore
colour) does not. If i = r, the angle of
refraction is 90º.
