4 Wave Parameters Wavelength (l) length or size of one oscillation Amplitude (A) strength of disturbance (intensity)Frequency (f) repetition
5 Wave Properties Waves are oscillations and they transport energy. The energy of a wave is proportional to its frequency.Fast oscillation = high frequency = high energySlow oscillation = low frequency = low energyThe amplitude is a measure of the wave intensity.SOUND: amplitude corresponds to loudnessLIGHT: amplitude corresponds to brightness
6 What is the Wave length?Measure from any identical two successive points510152025303540
7 What is the Wave length?Measure from any identical two successive points510152025303540= 20
8 What is the Wave length?Measure from any identical two successive pointsThere are 4 complete oscillations depicted hereONE WAVE = 1 COMPLETE OSCILLATION510152025303540= 20
9 FrequencyFrequency = number of WAVES passing a stationary point per second (Hertz)
10 Frequency and PeriodFrequency (f) = number of oscillations passing by per secondPeriod (T) = length of time for one oscillationT = 1/f f = 1/TIf a source is oscillating with a period of 0.1 seconds,what is the frequency?f = 1/(0.1) = 10 HzIt will complete 10 oscillations in one second. (10 Hz)If a source oscillates every 5 seconds, its period is5 seconds, and then the frequency isf = 1/5 = 0.2 Hz.
11 Wave Speed Wave speed depends on the wavelength and frequency. wave speed v = l fWhich animal can hear a shorter wavelength?Cats (70,000 Hertz) or Bats (120,000 Hertz)l = v/f
12 Wave Speed v = l f Which animal can hear a shorter wavelength? Cats (70,000 Hertz) or Bats (120,000 Hertz)l = v/fHigher frequency = shorter wavelengthLower frequency = longer wavelength
17 Line of Sight Only sensitive to motion between source and observer ALONGthe line ofsight.
18 Doppler Effect for Light Waves Change in frequency of a wave due to relative motion between source and observer.c = l f speed of light = wavelength x frequencyc = 3 x 108 m/sE = hf = hc/l energy of a light wave, a photonof frequency (f) or wavelength (l)h = planck’s constant 6.63 x J-secA light wave change in frequency is noticed as a changein “color”.
19 Wavelength Doppler Shift l0 = at rest (laboratory) wavelengthl = measured (observed) wavelengthDl = l - l0= difference between measured and laboratory wavelengthvr/c = Dl/l0vr = (Dl/l0)c radial velocity
20 Two Equal WavesUpon arriving in the same place, they add constructively
21 Constructive Interference Waves combine without any phase differenceWhen they oscillate together (“in phase”)
28 Two Slit Constructive Interference Path Length Difference = multiples of the wavelength l
29 Two Slit InterferenceSlits are closer together, path length differences change
30 Light or Dark? Path Length Differences = l, Waves arrive in phase Path Length Differences = 1/2 l, Waves arrive out of phase
31 Wave Properties Amplitude: Size of wave (perpendicular to direction of propagation)Proportional to Intensity(Sound loudness, Light brightness)Wavelength:l Size of wave (in the direction of propagation)Frequency:Number of waves passing a fixed position per secondf (cycles/second, Hertz)Wave Speed: v = l fFrequency increases Frequency decreasesEnergy increases Energy decreasesWavelength decreases Wavelength increases