Ch. 4 Waves, Sound, Light

1. Ch. 4 Waves, Sound, Light • Waves • A disturbance that moves through matter or space and carries energy • Matter does not move from place to place. • Energy transfers through the matter. • Think of the wave in a stadium. • The people (matter) do not change seats, but the energy travels around the stadium.

2. Compression Waves • AKA: Longitudinal wave • A mechanical wave (through matter only) • Causes particles to move back and forth along the same direction in which the wave is moving.

3. Lesson 1 Sound Waves • Sound Waves = Compression Waves • Cannot travel through empty space. • Mechanical waves • Travel fastest through solids, then liquids, then gases. • Travel fastest in warm mediums.

4. Sound intensity • Amount of energy carried by the wave. • Measured by the amplitude.

5. Amplitude • The amount of energy that a wave carries. • Tighter compressions on a compression wave equal greater energy and louder sound.

6. Compression Wave Wavelength

7. Frequency and Pitch. • Frequency • The number of wavelengths (compressions) that pass a point each second • Pitch • The human perception of the frequency of sound. • Sounds with a low pitch have a low frequency. • Sounds with a high pitch have a high frequency.

8. The Human Ear • Outer Ear • Visible ear and ear canal. • Compression wave funnel • Cup your hand around your ear?

9. Middle Ear • Sound amplifier • Eardrum • Tiny membrane that acts like a drumhead and vibrates with the compression waves. • 3 smallest bones in the body • Hammer - Malleus • Anvil - Incus • Stirrup - Stapes

10. Inner ear • The sound converter • The amplified compression waves travel from the stirrup to the cochlea. • Cochlea • Fluid filled • Snail shell shaped organ lined with billions of tiny hair like structures. • convert compression waves into nerve impulses. • Nerve impulses travel through auditory nerve to brain where they are interpreted as sound. • Semi Circular Canals: Acts as device to keep a human balanced.

11. The Human Ear

12. Sound reflection • Reverberations • Echoes • Sounds that reflect • Echolocation • Process of locating objects by bouncing sounds off of them. • Bats, Dolphins, Whales

13. Wave Speed • Electromagnetic waves: light waves • Travel fastest: • Space • Air (gas) • Water • Transparent solid • Mechanical Waves: compression/transverse • Travel fastest: • Solids • Water • Air • Do not travel through space

14. Section 2 Light Waves

15. crest trough Transverse waves • A mechanical wave (Can only move through matter) • Causes particles to move back and forth at right angles to the direction of the wave motion. • Rock in a pond!

16. Electromagnetic Waves • Can travel through empty space, gases, liquids, and solids. • Two Transverse Waves: examples • Light waves • X rays • Wi-Fi • AM,FM radio signals • Remote controls • Contain electric transverse wave and a magnetic transverse wave

17. Electromagnetic Wave

18. Amplitude: brightness, energy, intensity!

19. wavelength Wavelength • The distance between two like points on a wave.

20. 1 second Frequency • The number of wavelengths that pass a point each second. • Count the crests or troughs • Count the compressions or rarefactions

21. 2 second • Frequency equals……. • 6 wavelengths / second • 6 λ / s • 6 hertz • 6 Hz

22. Light Waves are….. • Able to travel up to 185,000 miles/s in empty space. • Able to travel from the sun to earth (150 million km) in 8 minutes. • Able to travel the fastest in empty space and the slowest in solids. (glass)

23. The electromagnetic spectrum Increasing Energy Decreasing wavelength

24. R O Y G B I V ROY G BIV

26. E.M. Waves and examples • Radio waves • AM, FM, cell signals • Microwaves • Wi-Fi, Microwave ovens, gps signals, satellite signals • Infrared waves • Heat producing bodies, remote controls • Visible Light • ROY G BIV • Ultraviolet waves • UV rays, bacteria killing lights • X-rays • Gamma Rays • Nuclear bombs, sun’s energy

27. Interaction of Light and Matter • Transmission • Light traveling through a material • Transparent • Almost all light travels through for a clear image • Translucent • Most light travels through, blurry image • Opaque • Light waves do not pass through • Reflection • Light bouncing off a material • Absorption • Light changing to heat

28. Refraction • Waves travel at different speeds depending on the properties of the material they are traveling through. • Causes the wave to change direction.

29. normal Law of Reflection • The angle of the incoming wave will equal the angle of the outgoing wave.

30. Any light? Diffraction • The bending of waves around an object. • Do shadows have crisp edges? If so, when? • Shadow of hand on desk?

31. Diffraction: Look at the edges!

32. Sct. 3 Mirrors, lenses, the eye • 2 major types of mirrors/lenses • Concave • The surface is curved inward

33. Concave lenses • One or both surfaces are curved inward • Used to spread the light waves apart

34. Convex • Surfaces that are curved outward

35. Convex lens • One or both sides are curved outward

36. The human eye.

37. How we see! • Light waves reflect off of an object. • Reflected light waves enter eye through cornea. • Transparent convex layer of outer eye. • Waves pass through the pupil. • Opening in the eye controlled by the iris. • Waves then pass through the lens. • Flexible convex lens that changes shape to allow you to focus on near and far objects. • Lens focuses waves on retina. • Back wall of the eye.

38. Retina • Contains over a hundred million light sensitive cells. • Rods • Sensitive to dim light • Help us to see in darkness. • Cones • Enable us to see colors. • 3 types • Red/yellow • Green/yellow • Blue/violet

39. Image of rods and cones in retina.

40. Let’s see.

41. Nearsighted vs. Farsighted. • Nearsighted • Cannot see objects far away. • Image focused to NEAR to the lens. • Farsighted • Cannot see object that are close. • Image focused to FAR from the lens.

44. Color in our world • The color of the objects you see represents the wavelength that reflects. white light