Sound and Light

1. Sound and Light Chapter 14

2. Lesson 1 What is sound energy?

3. What is sound energy? • Sound is a form of energy that travels in waves. • All sounds have common characteristics that can be measured and described. • Sound can travel through solids, liquids, and gases.

4. What sound is… • Sound is a form of energy. Sounds occur when objects vibrate. A vibration is a kind of wiggle. It’s a quick back-and-forth movement. • Vibrations pass energy to the air that surrounds it, so the air vibrates too! Vibrations travel through the air as sound waves. • A sound wave is a disturbance that moves energy through matter. Sound waves carry sound energy. If the waves reach our ears, we hear the sound.

5. Types of Sound Waves • As sound waves move they set air particles into motion. The moving air particles form a pattern. • Areas with groups of particles that are bunched together swap with areas of particles that are far apart.

6. Types of Sound Waves • The part of the wave where the particles are bunched together is called a compression.

7. There are two major types of waves • Transverse Waves - the particles of the material move up and down, at right angles to a source. (Jump Rope) • Longitudinal Waves -the particles in the material move side-to-side, parallel to the source. (Slinky)

8. Frequency and Wavelength Waves travel in different ways. They can carry different amounts of energy. But, all waves have certain properties. Frequency and wavelength are two of those properties

9. Frequency and Wavelength • The frequency of a wave is the number of waves that pass a point in a certain amount of time. • The faster an object vibrates, the higher its frequency will be. • Frequency is often described as the number of complete cycles a wave makes in one second. • A cycle is a vibration.

10. Frequency and Wavelength • Most sounds consist of sound waves of several frequencies. • Wavelength is the distance between a point on one wave and a similar point on the next wave.

11. How Sound Travels • Sound waves need a medium in which to travel. A medium is any kind of matter. Gases, liquids, and solids are mediums through which sound waves can travel.

12. A sound wave travels at different speeds through different mediums. • Particles in most liquids move a little less quickly and bounce back less quickly than in a solid. • Particles in a gas, such as air, sound waves travel most slowly • Particles in most solids move quickly in response to a sound vibration.

13. If you were floating in outer space, you would be in complete silence! • Space is a vacuum, an empty place that contains no matter. Since there are no particles of matter, sound waves would not be able to travel to your ears.

14. Echoes • As a sound wave travels, if bumps into objects. • If it hits a hard, smooth surface, the wave bounces back. (if you shout your name into a cave, you will hear it repeated.) • The sound waves bounced off the cave walls and traveled back to you. (Echo) • Scientists can find out how deep the ocean is by measuring the amount of time it takes for a sound to be sent and received.

15. Lesson 2 How is sound made?

16. Vibrating objects produce all types of sounds. The way an object is made and the way it vibrates affect the type of sound we hear. The frequency and the amount of energy in the sound wave also affect the sound we hear.

17. Loudness • A shout is a lot louder than whisper, but what exactly is loudness? • Loudness is a measure of how strong a sound seems to us. • Loudness is related to the amount of energy in a sound wave.

18. Loudness • If you are far from the source of a sound, it will not sound as loud as if you were standing nearer to it. • The sound waves do not have far to travel to your ears, so they will sound loud. But, if you were across the street, the sound would be softer. • The sound waves do not lose some of their energy as they travel through the air. The energy just spreads out to cover a larger area.

19. Pitch • Another characteristic of sound is pitch. • Pitch is what makes a sound seem high or low. Pitch depends on a sounds frequency. • Objects that vibrate quickly (high frequency) have a high pitch. • Objects that vibrate slowly (low frequency) have a low pitch. The material of the object making the sound and it’s size and shape affect the sound you hear.

20. Stringed Instruments • Guitars, violins, harps, and other instruments make sound when a musician plucks, rubs, or hits the strings. This sends vibrations through the instrument. • The notes on a guitar depend on the length and thickness of the string and how tightly it’s stretched. • Tightening guitar strings makes the pitch higher and loosening them makes them lower. Sound waves travel slowest through the thicker, heavier strings. These strings play the vibrate slowest and play the lowest pitches. Waves travel more quickly through the thinner strings. They vibrate faster and have higher pitch.

21. Percussion Instruments • Drums, xylophones, and maracas are examples of percussion instruments. These makes sounds when you shake or strike them. • When you hit a drum, the skin on the top of the drum vibrates and produces sound.

22. Wind Instruments • The musician blows air through a hole in a wind instrument. This causes particles in a column of air to vibrate. • The shorter the instrument, the higher the pitch.

23. Piano • A piano has more than 200 strings. When you press a key a hammer strikes the strings. The strings vibrate and produce a sound. (Pressing the key harder does not change the frequency or pitch)

24. How we hearTurn to page 415 Middle Ear Outer Ear Inner Ear Eardrum Cochlea

25. Lesson 3 What is light energy?

26. LIGHT • Light has much in common with sound. Both are forms of energy. Both travel as waves. • The human eye can only see a tiny fraction of light energy.

27. Sources of Light • No light source is more important to us than the Sun. • What would Earth be like without it? Turn and talk with your partner. • People, plants, and animals could not survive. • Long ago, humans discovered that they could make their own light. The discovery of fire opened up a whole new world. • People could light a campfire and stay warm, cook food, or work after dark.

28. Shadows • If you hold your hand in front of a wall and then shine a flashlight on it, a hand shaped shadow will show up on the wall. Your hand blocks the path of light rays. A shadow, or dark area, appears where the light rays cannot reach the wall. • Light travels in straight lines called rays that fan outward from the source of the light. You can easily see how light travels by looking at a shadow.

29. Shadows • The size of the shadow can change. If you hold your hand very close to the wall, your shadow will be about the same size as your hand. If you move your hand away from the wall and closer to the flashlight, the shadow will be larger than your hand. • The angle that the light strikes the object also affects the size of the shadow. • Remember our shadow activity outside? Around noon, when the Sun was highest, our shadow was short. Early in the morning and late in the day, when the Sun is lower, our shadow was long. Vusafe video on hand shadows and sand art

30. Light Waves We See • The light we can see makes up only a thin slice of the universe’s light energy. • Scientists refer to all forms of light energy as electromagnetic radiation. • Visible light, the light we see, is the most familiar form of electromagnetic waves. Light energy travels as a wave.

31. Light Waves • Like all waves, light waves have wavelengths and frequencies. • The human eye can see only the wavelengths and frequencies of the colors in the visible spectrum. • White light (like in a light bulb or the Sun) is actually a blend of all the colors in a rainbow. • Rainbow Colors= ROY G BIV • Red Orange Yellow Green Blue (INDIGO) Violet

32. Rainbow Colors= ROY G BIV Red Orange Yellow Green Blue (INDIGO) Violet • These colors always appear in the same order because of their wavelength and frequency. • As you move from left to right on the spectrum, wavelength decreases and frequency increases. Red light has the longest wavelength and the lowest frequency. Violet light has the shortest wavelength and the highest frequency

33. Electromagnetic Waves We Cannot See • Most of the waves in the electromagnetic spectrum are not visible. • Radio waves, microwaves, and infrared waves are invisible because their wavelengths are too long for the human eye to see.

34. Lesson 4 How do light and matter interact?

35. Light may behave in different ways when it strikes matter. What happens depends on the type of matter the light waves strike. • Light rays travel in straight lines (as long as nothing is in the way!) • Light changes when it hits an object. • The light may pass through the object • They may reflect off the object • They may be absorbed by the object.

36. Light and Matter • Light waves reflect at least a little off most objects. • REFLECTION occurs when light rays bounce, or reflect, from a surface back to our eyes. • When looking in a mirror, the shiny surface reflects almost all the light rays that hit it. The rays reflect back to your eyes at the same angle. You see a clear image of yourself.

37. Light and Matter • Light waves can also be ABSORBED. • Absorption occurs when an object takes in the light wave. • After a light wave is absorbed, it becomes a form of heat energy.

38. Color and Light • We see colors because objects absorb some frequencies and reflect others. • This red shirt looks red because it reflects light rays of the red frequency. It absorbs light rays of other visible color frequencies. • This shirt absorbs: _OYGBV • This shirt reflects: Red

39. Black & White • Black and white are special cases. • When light hits a white t-shirt, all color frequencies in the visible spectrum are reflected. (when all colors blend, it looks white) • When light hits a black t-shirt, all color frequencies are absorbed. **On a sunny day, black objects feel warm because the light energy they absorb changes into heat energy.

40. Letting the Light Through • Materials can be grouped by how they react to light. • Materials that transmit nearly all the light rays them hit them are transparent. (Glass) *You can see what’s on the other side. • Materials that let some light rays pass through but scatter other rays are translucent. (Wax Paper) *Light passes through and you can see whats on the other side, but it’s blurry. • Materials that do not let any light pass through are opaque. (aluminum foil) *Reflects or absorbs light . You cannot see what’s on the other side.

41. How Light Changes Direction • Light can be transmitted, reflected, and absorbed. But that’s not all, light can also be bent! (Refraction) • Unlike sound, light does not need a medium to travel through. • Light travels more slowly in a gas (air). • Light travels through a liquid more slowly than through a gas. • Light moves most slowly through the tightly packed particles in solids.

42. Light rays refract, or bend, as they travel from air to water. That’s why this pencil looks broken. The picture of the pencil shows what happens when light that is moving through air strikes a transparent solid that contains a transparent liquid.

43. The Human Eye • The human eye is a fluid-filled ball with a bony area around it. • A transparent covering protects the front of the eye. The covering also refracts light that enters the eye. • A doughnut-shaped muscle called the iris is behind the covering. • The iris is the colored part of the eye. • The dark opening in the center of the iris is called the pupil.

44. The Human Eye The rays form an upside-down image on the retina at the back of the eye. The light that enters then passes through the lens of the eye. The lens refracts the light rays even more. Lens The iris controls how much light enters the eye. In bright light=iris closes and pupil gets smaller In dim light= iris opens and pupil gets larger Cells in the retina change the light into signals that travel along the optic nerve to the brain. Then you see a right-side up image.

45. Lenses • Lenses are curved pieces of clear glass or plastic that refract light that passes through them. • Lenses can be used to help people see things that are very small or very far away. • There are two main types of lenses: CONVEX and CONCAVE.

46. Convex Lenses • A convex lens is thicker in the middle than at the edges, somewhat like a football. • When light passes through a convex lens, the light rays bend in toward the middle of the lens. • The bent light rays come together and meet at a point on the other side of the lens. • A convex lens can magnify things, or make them look larger. (magnifying glasses or microscopes)

47. Concave Lens • A concave lens is thinner in the middle than at the edges. • When light passes through a concave lens, the light rays bend out toward the thicker edges of the lens. The light rays spread apart. • So the object appears smaller than it really is.