Frequency and Types of Waves

Review: Features of a Wave A crest is the highest point on a wave. A trough is the lowest point on a wave. The wavelength is the distance, in meters, for one complete cycle of the wave. Crest to crest or trough to trough. The amplitude is the height of a wave crest or depth of a trough, as measured from its rest position. See pages 135 - 136 (c) McGraw Hill Ryerson 2007

Activity Catch a Wave Form p139

(c) McGraw Hill Ryerson 2007 Frequency Frequency is the number of repetitive motions, or oscillations, that occur in a given time. Frequency is usually measured in hertz (Hz). When the frequency of a wave increases the wavelength decreases. This is called an Inverse Relationship. This is called an Inverse Relationship See page 136 (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Bill Nye: Waves https://www.youtube.com/watch?v=R89dJP5v1Tg (c) McGraw Hill Ryerson 2007

Calculating Frequency Frequency can be calculated using the following equation: frequency = cycles/seconds Use the above equation to find the frequency for each of the following: a) A hummingbird flaps its wings 120 times in 3 seconds. b) A DVD spins 35 times in 7 seconds. Go to the next slide to view the answers See page 138 (c) McGraw Hill Ryerson 2007

Calculating Frequency Frequency can be calculated using the following equation: frequency = cycles/seconds Use the above equation to find the frequency for each of the following: a) A hummingbird flaps its wings 120 times in 3 seconds. (40 Hz) b) A DVD spins 35 times in 7 seconds. (5 Hz) Take the Section 4.1 Quiz See page 138 (c) McGraw Hill Ryerson 2007

Waves Travel through different mediums The matter that waves travel through is called a medium (can be solid, liquid, gas) Some waves such as light waves, can travel through space where there is no medium. See page 137 (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Two Types of Waves Two types of waves that travel through a medium are: Transverse wave – matter in the medium moves perpendicular to direction of the wave. All types of electromagnetic radiation, including visible light, are transverse waves waves.  . Transverse wave See page 137 (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Two Types of Waves Compression wave – matter in the medium moves parallel to direction of the wave. Eg. sound waves (vibrations in pressure, and seismic P- waves (created by earthquakes and explosions). Compression wave See page 137 (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Summary Waves transfer energy through matter or space. Amplitude is the height of a waves crest or depth of a wave trough, as measured from its rest position. A wavelength is the distance over which the wave repeats. As the wavelength decrease, the frequency increases. Waves can differ in how much energy they carry and in how fast they travel. (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Practice Read pages 134-137 Calculating Frequency WS – due at the end of class (c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007 Practice Homework Read pages 134-137 Answer CYU p143 #1, 2, 3, 4, 7, 8. (c) McGraw Hill Ryerson 2007