1. Waves that Bend, Bounce, Twist, Squeeze, etc. 5.1.6 Diffraction, Reflection, Refraction

2. Huygen’s Principle 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

3. 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 to BEND AROUND THE CORNER.

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

5. 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.

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

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

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

9. SPECULAR REFLECTION DIFFUSE REFLECTION DIFFUSE REFLECTION DIFFUSE REFLECTION NEXT

10. 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 Medium 2 Wave Fronts Incident Ray Refracted Ray FAST SLOW Normal Medium 1

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

12. 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.

13. 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

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

15. End of 5.1.6