1. Sound and Light See and hear the wave action!

2. Sound Is Caused By Vibration In order for sounds to be heard, a medium must be available to vibrate Any substance that transmits sound is a medium A medium can be a solid, liquid, or gas Sounds travel best in solids, next best in liquids, and least best in gases Speed of Sound (per second) Air Approx. 340 meters Water Approx. 1,400 meters Iron Approx. 6,000 meters *note: all at 15[deg]C

3. Transmitting Sound Sound is transmitted as periodic series of compressions and rarefactions Sound is always transmitted in longitudinal waves

4. Longitudinal waves are waves in which the medium moves back and forth in the same direction as the motion of the wave. Sound waves are of this type.

5. Transverse waves are what we most easily recognize as "waves". Ripples in water, vibration of a piano string, and the motion of the bars on the wave machine are all examples of transverse wave motion. In a transverse wave, the motion of the medium is perpendicular to the motion of the wave. To clarify, in a water wave, the actual water molecules move up and down while the wave moves horizontally. All light waves are transverse waves.

6. Characteristics of Waves Amplitude is the height of the wave Wavelength is the distance between any point on a wave and the same point on the next wave Frequency is the number of complete vibrations in a given time, it is measured in hertz, or cycles per second

7. Properties of Sound Pitch- how high or low a sound is, it depends on the frequency of vibration Ultrasonic- sounds with frequencies above those that humans can hear (>20,000 hertz) Doppler effect- the apparent change in frequency and pitch due to the motion of the sound or listener Intensity- the loudness of a sound, measured in decibels (human tolerance is 0-120 decibels)

8. Pitch Remember - slow is low! A mouse has a high pitch squeak A lion has a low pitch roar Don’t forget, you can demonstrate pitch by singing: do, re, mi, fa, so, la, ti, do!

9. Ultrasonic Waves Ultrasounds are at a pitch that is above a human’s hearing capabilities In other words, they happen without us hearing them Echolocation, medical ultrasounds, and dog whistles are all examples

10. Doppler Effect Stationary sounds have a regular pitch or the same frequency Approaching sources compress sound waves resulting in higher pitch and frequency As sources pass by, the waves spread farther apart resulting in lower pitch and frequency

11. Intensity Intensity deals with volume of sound The louder the sound, the higher the wave, or amplitude The quieter the sound, the lower the wave, or amplitude

12. Echoes Echoes are reflected sound Reflection is best on smooth surfaces To avoid echoes, soft or rough surfaces are used Bats and dolphins use echolocation to navigate We use ultrasound echoes in medicine Sonar uses echoes of sound waves to navigate

13. This diagram represents sound bouncing from a hard, flat surface like a brick wall. Notice how the sound waves can reflect off the surface and return to the source without interruption. Sound reflects or bounces off of matter in many ways:

14. The diagram below represents sound waves as they bounce off an irregular surface. Notice how the molecules scatter as they reflect off the irregular surface. They will collide with one another and cancel the echo effect.

15. The diagram below represents sound waves as they bounce off a soft surface such as a pillow. Notice that the pillow absorbs much of the sound energy and very little reflection takes place. Think about how a tennis ball would bounce off a pillow.

16. Sound is fast, but…. Sound travels in air at 3.4 kilometers per second! That’s fast, but light travels 300,000 kilometers per second! That’s why we see lightning first, and hear thunder last!

17. So What is Light? Visible Light – rainbows, fireworks, movies, lamps, the Sun Invisible Light – radio waves, microwaves, x-rays, infrared rays, ultraviolet rays, gamma rays All light begins in atoms as energy given off by photons The amount of energy in a photon determines the kind of light wave

18. Light Waves are Electromagnetic This means light can travel without a medium It can travel in the vacuum of space All light waves travel at the same speed, but at different wavelengths The speed of light is 300,000 kilometers per second!

19. Light Waves All light travels in transverse waves They are electromagnetic They all travel at the same speed Photons generate the two fields which are at right angles to each other (think of a jump rope)

20. The Visible Spectrum Consists of red, orange, yellow, green, blue, indigo, and violet Red has the lowest frequency and largest wavelength Violet has the highest frequency and smallest wavelength

21. Sources of Light Luminous objects – make their own light like the sun, fire, fireflies, stars Illuminated objects – reflect light to us like the planets, moon, plants, even other people!

22. When Light Strikes Transparent – light passes straight through (saran wrap) Translucent – light passes through, but is scattered (wax paper) Opaque – light is blocked (aluminum foil)

23. Reflection The type of surface light strikes determines the kind of reflection Regular reflection is crisp and off of smooth surfaces such as a mirror Diffuse reflection is fuzzy and off of an uneven surface such as a lake with small ripples Diffused light is very important since it allows us to see things in the shade or in shadows!

24. Mirrors The most common reflecting surfaces are mirrors Plane mirrors Concave mirrors Convex mirrors

25. Plane Mirrors Are perfectly flat Images appear right- side-up Images appear behind the mirror Image is the same size as object Image appears flipped

26. Concave Mirrors Are curved inward Concentrate the light beam Images are upside- down Found in flashlights, car headlights, and telescopes

27. Convex Mirrors Are curved outward Spread out the light Have right-side-up images that are smaller Found in side-view and rear-view mirrors on cars Objects appear farther away than they actually are

28. Refraction When light passes from one medium to another and bends Light moves at different speeds through different mediums This is why a pencil looks bent when placed in a beaker of water

29. Bending and Separating Prisms bend light as it enters and leaves the prism Raindrops bend light when a rainbow is seen Light slows down and separates White light is separated into the different frequencies of light known as the rainbow or ROY G. BIV (red, orange, yellow, green, blue, indigo, and violet)

30. Lenses Any transparent material that refracts or bends light Convex lenses are thicker in the middle, light converges or comes together, enlarges images, these are found in your eye, cameras, magnifying lenses, binoculars Concave lenses are thicker at the edges, light spreads out or diverges, images are smaller, and they help sharpen images, these lenses are found in eye glasses for nearsightedness

31. How We See We see because our eyes refract light! Light enters our eyes through the cornea and then the pupil which is surrounded by the iris A convex lens behind the pupil then bends the light and makes it converge on the retina smaller and upside- down Muscles attached to the lens adjust to focus the light on the retina Nerves behind the retina transfer the image to the brain where it is flipped right-side-up

33. The Color of Light The color of an object is the color of light reflected back to the human eye, all other colors are absorbed by the object The color of a transparent object is the color of light that passes through the object White objects reflect all colors (that’s why we wear light colors or white in the summer, it’s cooler!) Black objects absorb all colors (that’s why we wear dark colors or black in winter, it’s warmer!)

34. So Why is the Sky Blue? As white light passes through the atmosphere it is scattered by particles of dust and gases The low frequency, larger wavelengths of red and yellow light methodically pass through the atmosphere while the high frequency, smaller wavelengths of blue light are bounced and scattered around the sky At sunrise and sunset the light must travel through the thicker atmosphere so you see some of that red and yellow light near the ground!