 # Unit 10 Waves Wave Properties Introduction to Wave

• Slides: 30 Unit 10 Waves & Wave Properties Introduction to Wave Properties A wave is … …a motion of disturbance Waves “propagate in 3 -dimensions”. Waves move through a medium – the particles do not MOVE WITH THE WAVE! A wave moves through the medium. The medium does not move WITH the wave motion. The particles in the medium vibrate! http: //www. youtube. com/watch? v=b. Efrt. AOMuvk (1: 26) General Wave Form crest Equilibrium Line trough There are 2 types of waves Transverse Wave Longitudinal Wave Particle vibration is perpendicular is parallel to wave motion Transverse Wave Particle vibration is perpendicular to wave motion Slow Motion Video of “Transverse Wave” • http: //www. acoustics. salford. ac. uk/feschools/waves/bungyvideo. htm • http: //www. acoustics. salford. ac. uk/feschools/waves/guitarvideo. htm Longitudinal Wave Particle vibration is parallel to wave motion Slow Motion Video of “Longitudinal Wave” http: //www. acoustics. salford. ac. uk/feschools/wa ves/slinkyvideo. htm Label the following examples as transverse or longitudinal waves. longitudinal transverse Waves move through the medium! vibrates • The wave only _________ the particle, move • the particle does not _____ with the wave. There are 2 Categories of Waves Mechanical Waves Electromagnetic Waves Need a medium to Can travel without travel through. a medium For example, through gas, liquid through a vacuum or solids Sounds waves are… Mechanical waves! And an example of a longitudinal wave! Light waves are Electromagnetic Waves And an example of a transverse wave. Wave Speed Equation V=f λ velocity = frequency x wavelength c =f λ Speed of light = frequency x wavelength Sound needs a medium to travel Speed of Sound in standard air: v = 340 m/s Light can travel through a vacuum Speed of Light in a vacuum: c = 300, 000 m/s Frequency, Wavelength & Speed Which wave has the lower frequency? Which wave has the higher frequency? Which wave has the lower speed? Lower frequenc y Higher frequency Same Speed! Which wave has the higher frequency? Which wave has the higher wavelength? Which wave has the higher speed? higher frequenc y Same speed! higher wavelengt h What is the relationship between speed, frequency and wavelength? • The only way to change the speed of the wave is to To change the medium ____________. wavelength • A change in the frequency will change _______. frequency • A change in the wavelength will change ______. Interference “The Superposition Principal” Show resultant wave and label each as constructive or destructive interference. Constructive interference Complete destructive interference Destructive interference Which Wave is the Resultant Wave? This is the resultant wave! Which Wave is the Resultant Wave? Waves can “Reflect” Reflection occurs for both mechanical and electromagnetic waves. Sound and light waves can both reflect, but do so with various rules which will later be discussed with examples. Below are two common examples of sound and light reflecting. Sound waves can reflect causing what we know as an echo. Light waves can reflect causing what we know as a mirror effect. Standing Waves A wave pattern that results when two waves of the same frequency, wavelength and amplitude travel in opposite directions and interfere. Standing Waves have ‘nodes’ and ‘antinodes’ Antinode: A point in a standing wave which has the maximum amplitude. Node: A point in a standing wave which has no amplitude. How many nodes and antinodes are Create a Standing Wave! in each standing wave? 2 nodes, 1 antinode 3 nodes, 2 antinodes 4 nodes, 3 antinodes The Doppler Effect • An apparent change in frequency due to relative motion. High frequency Low frequency – Examples: • • Car music/horn as it drives by http: //youtu. be/h 4 On. BYrb. Cj. Y (0 -1 min) Police sirens Sonic Boom! (Breaking the sound barrier) Red shift and blue shift with light waves The Doppler Effect Large apparent wavelength Low Frequency wave Small apparent wavelength High Frequency wave