Characteristics of Waves Chapter 15

What are Waves? 15.1 Mechanical Waves – 2 Types of Mechanical Waves Requires matter (medium) to carry energy Mediums can be gases, liquids, or solids. produced when a source of energy causes a medium to vibrate Ex: sound wave, water wave 2 Types of Mechanical Waves Transverse – move perpendicular (water) Longitudinal – move parallel (Sound)

Waves and Energy Waves travel through water, but they do not carry the water with them. WAVE TYPE WAVE MOVEMENT mechanical – requires matter to travel Ex. sound 1. transverse- move at right angles Ex. light electromagnetic- does not require a medium to travel Longitudinal- moves parrallel

- Wave Action Most waves form when winds blowing across the water’s surface transmit their energy to the water.

Waves that move the medium at right angles to the direction in which the waves travel are called transverse waves.

Longitudinal waves move the medium parallel to the direction in which the waves travel.

- What Are Waves? Longitudinal Waves The compressions of a longitudinal wave correspond to the crest of a transverse wave. The troughs correspond to rarefactions.

Properties of Waves 15.2 4 Properties of Waves Amplitude Wavelength Frequency Speed The distance the medium rises depends on the amplitude of the wave The more energy a wave has the greater its amplitude

Frequency Speed A wave that occurs every second has 1 Hz Speed = Wavelength x Frequency Frequency = Speed Wavelength = Speed Wavelength Frequency If a medium does not change the speed of the wave is constant If you increase the frequency of a wave, the wavelength decreases

Amplitude, Wavelength, and Frequency

Calculating Frequency - Properties of Waves Calculating Frequency Practice Problem A wave has a wavelength of 2 mm and a frequency of 3 Hz. At what speed does the wave travel? (2 mm)(3 Hz) = 6 mm/s

Calculating Frequency - Properties of Waves The speed of a wave on a guitar string is 142 m/s and the frequency is 110 Hz. What is the wavelength of the wave? Calculating Frequency (142 m/s)/(110 Hz) = 1.3 m

Interactions of Waves 15.3 4 Interactions of Waves Reflection Refraction Diffraction Interference Constructive Interference Destructive Interference

Reflection All waves obey the law of reflection

Refraction When a wave enters a new medium at an angle, one side of the wave changes speed before the other side, causing the wave to bend. Bending only occurs when the wave enters the new medium at an angle, causing one side of the wave to enter the medium first

Diffraction When a wave moves around a barrier or through an opening in a barrier, it bends and spreads out.

constructive interference An adding of energies Amplitude increases when they meet

destructive interference Subtracting of energies The part of the wave that has the greatest amplitude wins

Standing Waves Standing Waves Nodes Caused by destructive interference zero amplitude Caused by destructive interference Antinodes Maximum amplitude Caused by constructive interference

Seismic Waves 15.4 3 Types of Seismic Waves P Waves S Waves P waves Surface Waves P Waves Longitudinal Move faster than other seismic waves S Waves Transverse Cannot travel through liquid Cause most severe ground movement

Earthquakes that occur underwater, like the one off the coast of Chile in 1960, can produce huge surface waves on the ocean called tsunamis.

Graphic Organizer Waves Transverse Longitudinal Crests Troughs can be can be Transverse Longitudinal contain contain contain contain Crests Troughs Compressions Rarefactions

Chapter Quiz