1. Announcements: Homework is due today – Make two separate piles
Vocab quiz is on Thursday
Lab tomorrow

2. Waves that Bend, Bounce, Twist, Squeeze, etc.
Diffraction, Reflection, Refraction

3. Huygen’s Principle of Diffraction
WAVELET – a small source of circular waves.
Lined up next to one another they will produce a…
WAVE FRONT – represents a wave crest.
The direction in which these travel is shown by a…
WAVE RAY – shows the direction of a wave’s travel. λ

4. Phenomenon #6 – Diffraction
When a barrier blocks part of a wave front only part of the wave will pass. The wavelet on the corner will express its curvature.
The wave rays BEND AROUND THE CORNER.

5. Single Slit Diffraction
Waves bend around BOTH corners.
The amount of bending depends on the relationship between WAVELENGTH and OPENING SIZE.
λ << opening
λ ≈ opening
Note that
wavelength
does NOT
change as
the waves
pass through!

6. Double Slit Diffraction
When a wave-front passes through two slits at the same time it bends through both slits and the wave-fronts interfere.

7. Reflection Revisited Regular (Specular) Diffuse Flat surfaces
Highly reflective
(ex. mirror, water)
Irregular surfaces
Most surfaces
(ex. paper, wood)

8. DIFFUSE REFLECTION
light from sun
to mountains
to your eye
DIFFUSE REFLECTION
light from sun
to buildings
to your eye
SPECULAR REFLECTION
light from Sun
to buildings
to water
to your eye
NEXT

9. The water is not flat enough for specular reflections in this picture
DIFFUSE REFLECTION
from all surfaces
The water is not flat enough for
specular reflections in this picture
NEXT

10. DIFFUSE
REFLECTION
SPECULAR REFLECTION
DIFFUSE
REFLECTION
DIFFUSE
REFLECTION
NEXT

11. Phenomenon #7 – Refraction
When a wave-ray passes from one medium into another it will bend due to the difference in SPEED between the two mediums.
Slow  Fast
Bends AWAY FROM NORMAL
λ INCREASES
Fast  Slow
Bends TOWARD NORMAL
λ DECREASES
Incident
Ray
Normal
Medium 1
Wave
Fronts
FAST
SLOW
Medium 2
Refracted
Ray

13. Phenomenon #8 – Polarization
A polarizer only allows waves with particles vibrating in a specific direction to pass.
This only works for TRANSVERSE waves.

15. Polarization optical illusions

16. Practice 3. Which wave phenomenon relates to…
apparent bending of a pencil in a cup of water.
bouncing of light off a mirror.
bending of water waves as they pass a dock.
selective filtering of light passing through sunglasses.
apparent change in frequency due to a moving source.
production of nodes and antinodes.
vibrations produced at a medium’s natural frequency.
meeting of two waves in a medium.
REFRACTION
REFLECTION
DIFFRACTION
POLARIZATION
DOPPLER EFFECT
STANDING WAVES
RESONANCE
INTERFERENCE
NEXT

17. Practice
1. A wave with a wavelength of 3.0 meters passes through an opening that is 0.02 meters wide. Which statement best describes what will happen to the wave? λ > Opening (1) The wave fronts will not bend. (2) The wave fronts will bend to a large degree. (3) The wave fronts will bend, but only slightly. (4) The wave will be completely stopped and will not pass.

18. Practice
2. Which combination will produce the least degree of diffraction? (1) a wavelength of 2.0 m through an opening of 1.0 cm (2) a wavelength of 30 m through an opening of 2.0 m (3) a wavelength of 2.0 m through an opening of 25 m (4) a wavelength of 5.0 nm through an opening of 45m

19. End of 5.1.6