Waves and Energy
GK-12 UCLA NSF
Meghedi Babakhanian
●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
●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?
Anatomy of a Wave
CREST
TROUGH
AMPLITUDE
WAVELENGTH
●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
●LongitudinalThe 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
●What type of wave is an ocean wave?
Waves
Key Terms
●Spherical wave propagation:
Intensity Calculation
area
Power
areatime
Energy
Intensity
24 r
PowerIntensity
●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
c
pressureIntensity
2
Effect of temperature on properties of air
Temperature in °C
Speed of soundc in
m·s−1
Density of airρ in kg·m−3
Acoustic impedanceZ in N·s·m−
3
+35 351.88 1.1455 403.2
+30 349.02 1.1644 406.5
+25 346.13 1.1839 409.4
+20 343.21 1.2041 413.3
+15 340.27 1.2250 416.9
+10 337.31 1.2466 420.5
+5 334.32 1.2690 424.3
0 331.30 1.2922 428.0
−5 328.25 1.3163 432.1
−10 325.18 1.3413 436.1
−15 322.07 1.3673 440.3
−20 318.94 1.3943 444.6
−25 315.77 1.4224 449.1
● ρ (Density of medium) ● c ( speed of medium)● ρ c (air @ room temp 20 °C) = 413.3 N·s·m−3
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.
●Basic function of an oscilloscope: To display voltage vs. time. ● Voltage: usually on the vertical axis ● Time: usually on the horizontal axis.
Oscilloscope
●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
● 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
●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