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Please, read over these questions :

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1 Please, read over these questions :
When speed increases, what happens to kinetic energy? Which is moved by a wave, energy or matter? Do EM and Thermal energy need a “medium” to travel? Give an example to explain your answer. What are the three major divisions of wave types? List the six wave properties.

2 Waves and Energy Transfer Notes
General Physics – April 27, 2017

3 Energy Transfer Have you ever ridden a wave on a surf board, boogie-board, or merely body surfed? When you “catch a wave” you gain speed and just stay ahead of the “breaking-surf.” As you gain speed, your body’s kinetic energy increases (KE = ½ mv2)!

4 Energy Transfer, continued
Does the water move with the wave? “The [energy] is much quicker than the water, for it often happens that the wave flees the place of its creation, while the water does not…” – Leonardo Da Vinci In other words, the wave moves on – the water does not. Waves move ENERGY not MATTER!

5 Energy is transferred by waves & particles.
Both particles and waves transfer energy. If I throw a ball (particle) at a target, the target will gain Kinetic Energy – but the ball (particle) has moved. If I tie a rope to a target and shake the rope (wave), the target will gain Kinetic Energy – However, the rope has not left my hand. Hence, energy is transferred by both particles and waves!

6 Types of Waves Mechanical and Fluid Energy needs a “medium” to travel through. Electrical (magnetic) and Thermal Energy does NOT need a “medium” to travel. Mechanical and Fluid waves can be divided into three types: TRANSVERSE, LONGITUDINAL, & SURFACE.

7 Wave Properties Amplitude Wavelength = l Frequency = f = 1/T
Period = T = 1/f Wavespeed = lf Wavespeed = d/t WaveEnergy = hf h = 6.626x10-34 J/Hz Planck’s Constant Frequency

8 Wave Property Units: Amplitude in meters Wavelength in meters
Frequency in cycles per second or Hertz (Hz) Period in seconds Wavespeed = meters per second WaveEnergy = Joules

9 Wave Speed = v = d/t = lf = l / T
Example #1: A sound wave is produced 515 meters away and is heard 1.5 seconds later. What is its speed? What is its wavelength if its frequency is 436Hz? What is its period?

10 Example #1: A sound wave is produced 515 meters away and is heard 1
Example #1: A sound wave is produced 515 meters away and is heard 1.5 seconds later. What is its speed? speed = distance / time = 515m/1.5s = 343.3m/s What is its wavelength if its frequency is 436Hz? Wavelength = speed/frequency = 343.3m/s / 436 Hz Wavelength = 0.79 meters What is its period? Period = 1 / frequency = 1 / 436 Hz Period = seconds/cycle

11 YOUR TURN! Example #2: Mr. G shouts towards a student 685 m away. The student hears it 2 s later. What is its speed? If its sound wave has a wavelength of 0.750m, then what is its frequency? What is the wave’s period?

12 Example #2: Mr. G shouts towards a student 685 m away
Example #2: Mr. G shouts towards a student 685 m away. The student hears it 2 s later. What is its speed? speed = d / t = 685m / 2s = m/s If its sound wave has a wavelength of 0.750m, then what is its frequency? f = v / l = m/s / m = 457 Hz What is the wave’s period? T = 1 / f = 1 / 457 = seconds

13 Wave Speed = v = d/t = lf = l / T
Example #3: A typical light wave has a wavelength of 580x10-9 meters and a speed of 3x108 m/s. What is the frequency of the light wave and what is the light wave’s period?

14 Example 3, answered Given: l = 580x10-9 meters v = 3x108 m/s
Find: f and T Solution: f = v / l = 3x108 m/s / 580x10-9 meters f = 5.2x1014 Hz T = 1 / f = 1 / 5.2x1014 Hz = 2x10-15 seconds


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