Big Idea 10 :

1. Big Idea 10: Forms of Energy Description A. Energy is involved in all physical processes and is a unifying concept in many areas of science. B. Energy exists in many forms and has the ability to do work or cause a change.

2. Benchmark Number &Descriptor • SC.7.P.10.1 • Illustrate that the sun's energy arrives as radiation with a wide range of wavelengths, including infrared, visible, and ultraviolet, and that white light is made up of a spectrum of many different colors. • SC.7.P.10.2 • Observe and explain that light can be reflected, refracted, and/or absorbed. • SC.7.P.10.3 • Recognize that light waves, sound waves, and other waves move at different speeds in different materials.

3. WHAT’S a WAVE?

4. NATURE OF WAVES • Waves (Def.) – Adisturbance that transfers energy • Medium – Substance through which a wave moves through • Speed of Waves – Depends on the properties of the medium

5. What are the parts of a wave? Transverse wave • The crest = highest point on a transverse wave • The trough = lowest point on a transverse wave • The wavelength is the distance from one point on the wave to the next corresponding adjacent point • EX: Trough to trough • Crest to crest

6. What are the parts of a wave? Compressional (Longitudinal) Wave • Compression = Tightly coiled section • Refraction = Loose, less coiled section • Wavelength = the distance from one point on the wave to the next corresponding adjacent point

7. . . WAVELENGTH and FREQUENCY What is wavelength? What is wave frequency? • The distance from one point on the wave to the next corresponding adjacent point • The smaller the wavelength, the more times it will pass through a point in one second • The larger the wavelength, the fewer times it will pass through a point in one second • Frequency is the number of waves that pass through a point in one second. • The unit for frequency is waves per second or Hertz (Hz). • One Hz = One wave per second. • Wavelength and frequency are inversely related.

8. What is the amplitude of a wave? • Transverse Wave • Height of crest trough from standstill • Larger the height, greater the energy • Compressional Wave • Greater amplitude = Tighter coils • Less amplitude = Loose coils

9. KNOWLEDGE CHECK • How does the frequency of a wave relate to its wavelength? • Name two types of waves. • Name two parts of each wave. • How is amplitude of a longitudinal wave measured?

10. KNOWLEDGE CHECK • How does the frequency of a wave relate to its wavelength? The greater the frequency, the smaller the wavelength. • Name two types of waves? Longitudinal and Transverse • Name two parts of each wave. Longitudinal = Compression/Rarefaction Transverse = Crest/trough • How is amplitude of a longitudinal wave measured? Based on the tightness of the coils

11. LIGHT WAVES

12. We see things because they reflect light into our eyes: Homework

13. Electromagnetic Spectrum • Visible Spectrum – Light we can see • Roy G. Biv – Acronym for Red, Orange, Yellow, Green, Blue, Indigo, & Violet • Largest to Smallest Wavelength

14. Light • Our primary source of light is the sun. • Light travels in straight lines at a speed of 186,000 miles per second. • Light waves travel fasterthan sound waves! • Light energy from the sun travels through space, reaches earth, and some of it turns to heat energy and warms the earth’s air. • Light from the sun also travels to the cells of green plants (producers) and is stored as energy. • When light reaches an object, it is absorbed, reflected, or passes through it.

15. KNOWLEDGE CHECK • What is the order of the Electromagnetic Spectrum? • What is our major source of light energy? • Which travels faster, light or sound?

16. KNOWLEDGE CHECK • What is the order of the Electromagnetic Spectrum? ROY G. BIV (red, orange, yellow, green, blue, indigo, violet) • What is our major source of light energy? The Sun • Which travels faster, light or sound? Light waves

17. LIGHT INTERACTIONS How Waves React

18. Reflection • A bouncing back of a wave after it hits a barrier • Does not go through a barrier • Echo = reflection of a sound wave Reflected ray Incident ray Mirror

19. REFRACTION • Bend a wave at an angle as it hits a medium/barrier • Light waves -> Prism -> Rainbow • Light (colors) have a different wavelength; a prism breaks them apart.

20. Transparent objects: • The windows on a school bus • A clear empty glass • A clear window pane • The lenses of some eyeglasses • Clear plastic wrap • The glass on a clock • A hand lens • Colored glass • ALL of these are transparent. • We can see through them because light passes through each of them.

21. Translucent objects • All of these materials are translucent . • Allow some light to pass but the light cannot be clearly seen through. • Thin tissue paper • Waxed paper • Tinted car windows • Frosted glass • Clouds

22. Opaque objects • Heavy weight paper • Cardboard • Aluminum foil • Mirror, bricks, buildings • Your eyelids and hands • Solid wood door • All of these objects are opaque because light cannot pass through them at all. • They cast a dark shadow.

23. KNOWLEDGE CHECK • Name a material that is opaque and reflects light waves? • Name a material that is transparent and refracts the light waves? • Name a material that is translucent and scatters light waves?

24. KNOWLEDGE CHECK • Name a material that is opaque and reflects light waves? Mirror • Name a material that is transparent and refracts the light waves? Water • Name a material that is translucent and scatters light waves? Clouds

25. WHAT’S THAT I HEAR? SOUND WAVES

26. SOUND WAVES • We hear sound which usually travels through air. • Sound can travel through other mediums such as water and various solids. • Sound travels different speeds through different mediums. • Sound generally travels faster in a solid than a liquid and faster in a liquid than a gas. • The denser the medium, the faster sound will travel. • The higher the temperature, the faster the particles of the medium will move and the faster the particles will carry the sound.

27. What is sound intensity? • Sound intensity is the energy that the sound wave possesses. • The greater the intensity of sound the farther the sound will travel and the louder the sound will appear. • Loudness is very closely related to intensity. • Loudness is the human perception of the sound intensity. • The unit for loudness is decibels.

28. How is frequency related to pitch? • The pitch of a sound wave is directly related to frequency. • A high-pitched sound has a high frequency. • ex.screaming girl • A low-pitched sound has a low frequency. • ex. fog-horn • A healthy human ear can hear frequencies in the range of 20 Hz to 20,000 Hz. • Humans cannot hear below 20 Hz. Sounds below this frequency are termed infrasonic. • Sounds above 20,000 Hz are termed ultrasonic. • Some animals, such as dogs, can hear frequencies in this range in which humans cannot hear.

29. Loudness in Decibels

30. KNOWLEDGE CHECK • What type of matter does sound travel best through? • How does temperature affect the speed of sound? • What is the relationship between pitch and frequency?

31. KNOWLEDGE CHECK • What type of matter does sound travel best through? Solids • How does temperature affect the speed of sound? The higher the temperature, the faster the sound will travel. • What is the relationship between pitch and frequency? Pitch and frequency are directlyrelated.