Characteristics of Waves

1. Characteristics of Waves SI

2. What is a wave? • A disturbance through a medium as energy is transmitted through that medium • Energy is the ability to do work, therefore: • Sound waves do work on your eardrum • Light waves do work on your eye • The bigger the wave, the more energy it carries

3. Types of Waves: Mechanical Mechanical waves – waves that require a medium Mechanical waves travel fastest through solids because the particles of a solid are more tightly packed together

4. Types of waves: Electromagnetic Electromagnetic waves – waves that do not need a medium to travel Examples: • Visible light • Radio • Microwave • Infrared (IR) • Ultraviolet (UV) light • X ray • Gamma Ray

5. Shape of Waves: Transverse Transverse waves – simple sine curve • The motion of the particles in the medium is perpendicular to the motion of the wave • Light waves are transverse waves • Amplitude - The greatest distance that particles are displaced from their original resting positions or half the distance between the crest and the trough • Crests – highest points • Troughs – lowest points • Larger waves have larger amplitudes and carry more energy • Louder sounds have larger amplitudes

6. Shape of Waves: Transverse

7. Shape of Waves: Longitudinal Longitudinal waves -have compressions and rarefactions • The motion of the particles is parallel to the direction that the wave travels • Sound waves are longitudinal waves • Compressions – crowded areas, medium becomes more dense • Rarefactions – stretched out areas, medium becomes less dense

8. Shape of Waves: Longitudinal

9. Surface Waves • Move circular (combination of perpendicular and parallel motions)

10. More Wave Properties • Wavelength () - The distance between two identical parts of a wave • Period- The time required for 1 full wavelength of a wave to pass a certain point • Represented by “T” (units = seconds) • THINK – PERIOD OF TIME!!!!!!!! • Frequency - The number of cycles/wavelengthsper unit of time • Represented by “f” (units = Hertz (Hz)) • Frequency = 1/T

11. Frequency, Wavelength, and Energy • What happens to the wavelength as frequency increases? • What variables affect the color of light that you see? • Higher frequency = more energy and shorter wavelength…The more wavelengths per unit time, the more energy.

12. Wave Speed • Speed = wavelength / period, so… • Wave speed = frequency x wavelength • Wave speed depends on medium • They travel the fastest in solids than in air or water • Why? • In a gas, particles are farther apart so it takes longer for them to bump into each other • In liquids, particles are closer together so waves travel faster • In solids, particles are very close together so waves travel the fastest

13. Doppler Effect • Pitch is determined by frequency • Sound waves travel out from an object in wave fronts and hit your eardrum • Ambulance example: • When the ambulance moves toward you, the sound waves are compressed – so the waves hit your eardrum at a higher frequency – higher pitch • When the ambulance moves away from you, the sound waves are stretched out, so the frequency is lower – pitch is lower • Doppler effect can also happen in light and other types of waves