1. REFRACTION

2. I wasn’t going to jump anyway I think we are being watched!
Refraction is the Bending of Waves due to a Change in Velocity
Refraction is the Bending of Waves due to a Change in Speed as they travel between media.
I wasn’t going to jump anyway
I think we are being watched!
One would think that the boat would block your view.

4. Rootbeer Mug Refraction Demo - Paul G Hewitt (4:30)

5. REFRACTION IS A WAVE THING
Just thinking, no writing.
REFRACTION IS A WAVE THING
Think of the blue bars as a travelling ripple of light. (similar to water waves)
air
glass / water

6. REFRACTION FROM Medium 1 TO 2
Just thinking, no writing.
REFRACTION FROM Medium 1 TO 2
Waves travel SLOWER IN a DENSER MEDIUM
- Look at how close the wave fronts are.
Optically less dense medium (1)
Optically denser medium (2)
Wavelength REDUCED

7. LAWS OF REFRACTION Θ1 = angle of incidence Θ2 = angle of refraction
Back to the writing.
LAWS OF REFRACTION
Θ1 = angle of incidence
Θ2 = angle of refraction
Incident ray
normal 1
Refracted ray 2
Fact 1. The incident ray, the refracted ray and the normal are all connected to the transition from one medium to another.
Fact 2. For two given media, the angle in the denser (slower) medium for light will be smaller.

8. happens when a light ray
Incident ray
normal
Refracted ray 1 2
θ is smaller in the more
dense medium.
Fact 3. We say
that the ray refracts
towards the Normal.
What do you suppose
happens when a light ray
travels from a denser
to a less dense medium?

9. a) Which medium is more optically dense? b) Which medium allows
Thinking
QUESTION
water
glass θ
300
Follow the light ray and examine the angles.
a) Which medium is more
optically dense?
b) Which medium allows
light to travel faster?

10. Violet light refracts more in glass than red light
ROYGBIV, the spectrum of light music video (optional if you’re good)

11. total internal reflection
critical
angle
Critical Angle YouTube Video

12. A little light is also reflected.
Remember: When light travels from an optically denser medium to a less dense medium, rays are bent away from the normal. Write the yellow bits and add to the ray diagrams.
For a larger angle of incidence, more light is reflected as well as the refracted ray being bent further from the normal
When the critical angle, c, is reached it produces an angle of refraction of 900
Diagram 1: c
A little light is also reflected.
Diagram 2:
Diagram 3:
Diagram 4:
For angles of incidence greater than the critical angle,
TOTAL INTERNAL REFLECTION occurs. θ θ
Note: The angle of incidence
= The angle of REFLECTION

13. 1 2 C
Critical angle depends upon the optical densities of the two materials.
I’ll say it again:
“At the critical angle the angle of refraction is 90 degrees and there is no light getting into the second medium. “ – Ray D. Igram

14. For Water into air Critical angle = 48.80 For Glass into air C = 41.802 C
For Water into air
Critical angle = 48.80
AIR
Glass
For Glass into air
How is this possible?
C = 41.80

15. Critical Angle for common glass = 420
Two Common Instruments that Use Critical Angles:
PERISCOPE – two right isosceles prisms
observer
Total internal reflection
420
420
Critical Angle for common glass = 420

16. Critical Angle for common glass = 420
PRISMATIC BINOCULARS
Objective lens
Eyepiece lens
420
Critical Angle for common glass = 420

17. Hot Desert Sand
air layers
THE MIRAGE
Water
for my hump!
Air layers closer to the sand are hotter and less dense. Light from the sky is successively refracted until a critical angle is reached and then total internal reflection occurs.
A mirage "water" illusion is seen because the mind initially interprets the light rays reaching our eyes as having come along a straight path originating from the ground. Thus, the image of that patch of sky we see "on the ground" is interpreted as a surface "pool of water."

18. FIBRE OPTICS Diameter around 50 μm
core
cladding
Light trapped in fibre core
STEP INDEX FIBRE
Diameter around 50 μm
A light bounces back and fourth so that the light always hits at the critical angle or greater than the critical angle.
This means that light never escapes from the core.
The light signal isn’t lost over huge distances.

19. ENDOSCOPE A use for bundles of fibre optic cable:
End probe containing coherent bundle, incoherent bundle, lens and surgical instruments
Controls
Eyepiece
Light injected here
ENDOSCOPE
This is an endoscope image of the inside of the throat. The arrows point to the vocal chords

20. Wow look at the variation in refraction!
Rainbows
Wow look at the variation in refraction!
Rainbows explained on YouTube
Skier will see red at the top of the rainbow, and blue at bottom.

21. LIKE SO!
In second rainbow pattern is reversed

22. Observing the Rainbow
If a raindrop high in the sky is observed, the red ray is seen
A drop lower in the sky would direct violet light to the observer
The other colors of the spectra lie in between the red and the violet
Rootbeer mugs and refraction video.
Just because Paul G. Hewitt rocks.