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Label the key terms MORE THAN ONCE: crest, trough, amplitude, wavelength

Do Now: Take a clicker. Observe the demo. You have 3 minutes with your group to draw what you see and LABEL the following terms correctly on your drawing: crest Trough Amplitude Wavelength

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Label the key terms MORE THAN ONCE: crest, trough, amplitude, wavelength

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  1. Do Now: Take a clicker. Observe the demo. You have 3 minutes with your group to draw what you see and LABEL the following terms correctly on your drawing: • crest • Trough • Amplitude • Wavelength • HW:p. 388 #1-9, 11-13 ….Read & Study the corresponding sections in CH. 25 (7 points – ½ point per problem, and 1 point for a randomly graded one) • PLEASE check the Lost & Found. Claim what is yours – BE HONEST AND DON’T STEAL. Anything left at the end of the year will be trashed or donated

  2. Label the key terms MORE THAN ONCE:crest, trough, amplitude, wavelength TROUGH is the lowest point on a wave

  3. Label the key terms MORE THAN ONCE:crest, trough, amplitude, wavelength CREST is the highest point on a wave

  4. Label the key terms MORE THAN ONCE:crest, trough, amplitude, wavelength Amplitude is the distance from the midpoint to the crest or the midpoint to the trough

  5. Label the key terms MORE THAN ONCE:crest, trough, amplitude, wavelength Wavelength is the distance between 2 IDENTICAL, CONSECUTIVE PARTS of a wave

  6. Label the key terms MORE THAN ONCE:crest, trough, amplitude, wavelength • CREST is the highest point on a wave • TROUGH is the lowest point on a wave • Amplitude is the distance from the midpoint to the crest or the midpoint to the trough • Wavelength is the distance between 2 IDENTICAL, CONSECUTIVE PARTS of a wave

  7. What is a wave? • A vibration or disturbance. • A wiggle in space and time • Any other definitions? • SOUND & LIGHT are forms of energy that travel in waves. • However, they travel in different types of waves… to be discussed later!

  8. Frequency (ƒ) • How OFTEN /FREQUENTLY a wave happens • # of wave cycles OR wavelengths in one second. • Measured in Hertz (Hz). • 1 Hz = 1 wavelength OR wave cycle per second • “When a frequency is too high, it HERTZ your ears!” • Becca Caplinger

  9. Period (T) • The TIME PERIOD for ONE wavelength / wave cycle • A period is the time it takes for 1 complete wave length / wave cycle • 1 cycle = 1 complete trip • 1 trip back & forth, crest to crest • Around and back to the same point (1 wavelength) • 1 wave = 1 cycle • Measured in seconds

  10. They are INVERSES of each other!!! • Clapping demo

  11. See board for formula in symbols! period = 1 frequency frequency = 1 period

  12. Analogy • One class PERIOD at RHS is 90 minutes. • (time it takes for 1 class = 90 minutes…that’s the PERIOD) • You have 1 class per 90 minutes, which is how FREQUENTLY you have classes T = 90 minutes f = 1 class 90 minutes • They are inverses!

  13. True or false: When a wave travels in a medium (material) the medium moves with the wave. • True • False • Not enough info • Not quite sure

  14. DO THE WAVE demo • Write down your observations…. • It’s not the medium that moves with the wave… it is the ENERGY that is transmitted! The energy moves!

  15. But wait – what’s a medium? • It’s not someone who summons spirits. • It’s synonym for material! • Different types of solids, liquids, and gases are all examples of mediums. • Changing the TEMPERATURE changes the medium: • Example: temperature in this room vs temp. outside: different temps, different mediums (even though they are both air!)

  16. 25.4 Wave Speed The speed of the wave depends on the ______________________________ through which the wave moves • If the MEDIUM doesn’t change, then the WAVESPEED doesn’t change! (KEY POINT) Medium or material SEE THE BOARD!

  17. You SEE lightening and THEN hear thunder. What does this tell you about the speed of sound vs. the speed of light? • Light is faster • Sound is faster • They are the same speed • Not enough info • Not quite sure

  18. Does wave speed depend on AMPLITUDE (hint - check the formula)? • Yes • No • Not enough info • Not quite sure

  19. Slinky Wave Lab • Safety Rules: • All labs must be completed with the slinky FLAT on the floor • Damaging, twisting, tangling, or otherwise rendering the slinky useless will result in one or more of the following: • Write up • Loss of lab privileges • You buying me a new slinky • Have fun! Stopping with 5-10 minutes left for a clicker exit!

  20. Observe the demo: is this a transverse or longitudinal wave? • Transverse • Longitudinal • Not enough info • Not quite sure

  21. Observe the demo: is this a transverse or longitudinal wave? • Transverse • Longitudinal • Not enough info • Not quite sure

  22. These waves travel towards each other… the result is..? • Constructive interference • Destructive interference • Not enough info • Not quite sure They CONSTRUCT a bigger wave!

  23. These waves travel towards each other… the result is..? • Constructive interference • Destructive interference • Not enough info • Not quite sure They DESTRUCT The wave!

  24. 0.5 1 1.5 2 2.5 3

  25. What do your answers tell you about wavelength and frequency? Are they directly or inversely proportional? • Directly • inversely • Not enough info • Not quite sure

  26. Inversely!!! λ f = ν = λf When the waves were MORE FREQUENT, You observed SHORTER WAVELENGTHS!

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