1. light slows down (v<c)
Light Refraction the bending of a light ray as it passes from one medium to another
air
glass
light slows down (v<c)

2.  = angle to the normal (0)
Snell’s Law
n1sin1 = n2sin2
 = angle to the normal (0)
n = refractive index (no unit)

3. PhET Bending light applet

4. Partial reflection
(inverted)
Refraction 1
Refraction 2

5. Refraction Island off Jaffna Sri Lanka
Slow
Shallow
Fast
Deep

6. Refraction Fast Slow Deep Shallow
The waves slow down (bunch up) in the shallow water.
Fast
Deep
Slow
Shallow

8. Fast
Deep
Slow
Shallow
NCEA Standard - harder!

9. 1 2 Snell’s law calculates angles of refraction. n1sin1 = n2sin2

12. Success…
Do 3+ problems
Get confidence by # 3…

13. A series of waves are travelling through water in a shallow pool and passes into a deeper region as shown.
Sketch the waves as they travel through the deep region. 1
shallow
deep

14. DOT line (direction of Wave travel) – Thanks to Michael Hatton
shallow
deep

15. Shallow water
Deep water

16. 2 normal Deep water Shallow water
Roy and Sally spent time on a beach watching the incoming waves. The diagram below shows wavefronts as they approach shallow water. The waves travel slower in shallow water
normal
Shallow
water
Deep
Shallow water
Deep water
NZQA 2
Copy the diagram and draw an arrow showing the wave direction and the refracted wavefronts in the shallow region
Clearly explain why the waves behave as you have drawn them in the diagram above.
The part of the wave front that hits the shallow region slows down and moves at a slower speed through the shallow water.
The part of the wave front that is still in deep water is still moving at the same fast speed.
It is the different speeds of the wave front that causes the wave to swing towards the normal

17. or The right-hand end of the waves slow down
before the left-hand end. This causes the wave front to swing towards the normal.

18. Hz or s-1 State two possible units for frequency
normal
Shallow
water
Deep
The part of the wave front that hits the shallow region slows down and moves at a slower speed through the shallow water as shown in the diagram.
NZQA
State what happens to the frequency and wavelength of the waves as they pass from deep to shallow water.
The frequency stays the same
Wavelength decreases as speed decreases because frequency equals velocity ÷ wavelength. i.e., re arranged from v = f
There are 8 complete waves passing a fixed point in 20 s.
Calculate the frequency of the waves.
State two possible units for frequency
Hz or s-1
The speed of the waves in shallow water is 2.8 m s–1. Calculate the wavelength of these waves

19. 3
assume f1 = f2 !