1. Waves and Energy GK-12 UCLA NSF Meghedi Babakhanian

2. ● List as many types of waves you can think of. ● What do waves transfer? ● In this picture, what is happening to the gravitational potential energy of the drop? What are Waves? San Diego Unified School District Physics 1,2 Core Laboratory Activity - Lab 17: Waves

3. ● Sound waves, visible light waves, radio waves, microwaves, water waves, sine waves, cosine waves, stadium waves, earthquake waves, waves on a string, slinky waves - ALL types of Waves! ● Waves transfer ENERGY!! ● Gravitational potential energy of a water drop turns into kinetic energy, which transfers energy in the form of a WAVE! What are Waves?

4. Anatomy of a Wave CREST TROUGH AMPLITUDE WAVELENGTH

5. ● Transverse The motion of the medium is at right angles to the direction in which a wave travels Stretched strings of musical instruments, electromagnetic waves, S-waves in earthquakes ● Longitudinal The particles of the medium move back and forth in the same direction in which the wave travels Sound waves, P-waves in earthquakes Two Types of Waves

6. ● What type of wave is an ocean wave? Waves

7. ● Frequency – Number of cycles per unit of time (s), measured in Hz Frequency = 1/Period Period = 1/Frequency ● Hz – One cycle per second ● Wave Speed = wavelength * frequency ν=λfν=λf Wave speed depends on the medium through which the wave moves. Key Terms

8. ● Spherical wave propagation: Intensity Calculation

9. ● Using voltage: ● You see voltage vs. time on the oscilloscope ● You can think of it as sound wave pressure vs. time. Intensity Calculation Using Oscilloscope Effect of temperature on properties of air Temperature in °C°C Speed of soundc in m· s −1m· s −1 Density of airρ in kg·m −3 Acoustic impedanceZ in N·s·m −3N +35351.881.1455403.2 +30349.021.1644406.5 +25346.131.1839409.4 +20343.211.2041413.3 +15340.271.2250416.9 +10337.311.2466420.5 +5334.321.2690424.3 0331.301.2922428.0 −5328.251.3163432.1 −10325.181.3413436.1 −15322.071.3673440.3 −20318.941.3943444.6 −25315.771.4224449.1 ● ρ (Density of medium) ● c ( speed of medium) ● ρ c (air @ room temp 20 °C) = 413.3 N·s·m −3 N

10. Conclusion We are constantly interacting with waves Waves carry energy Light and S-waves are examples of transverse waves. Sound and P-waves are examples of longitudinal waves.

11. ● Basic function of an oscilloscope: To display voltage vs. time. ● Voltage: usually on the vertical axis ● Time: usually on the horizontal axis. Oscilloscope

12. ● Display screen of the oscilloscope: ● Grid of black lines ● Division - Each square in this grid is known as a “division”. ● Two main things that you will change on the oscilloscope: ● Number of volts that each division represents ● length of time each division represents. Oscilloscope

13. ● Practice with me: ● Look at the front of oscilloscope and find the knobs that say: ● “Volts/Div” and “Time/Div”. ● Try twisting the knobs and see what happens. Oscilloscope

14. ● Voltage: ● When you turn the knob on “Volts/Div”, you’re changing how many ___________each square represents. ● Example: if the setting is 10 Volts/Div, each square represents _____ V. ● Time: ● When you turn the knob on “Time/Div”, you’re changing how many ___________each square represents. ● Example: If the setting is 1 ms/Div, each square represents _____ millisecond. Oscilloscope