Slinky Activity With a partner, each person holds the slinky firmly (Don’t let go!!) One person shake the slinky back and forth (like a Transverse wave) trying to form the waves to the right. Document how much energy it took to form each wave. Questions A- What did you have to do to make more waves appear? B- What do these waves represent? C- Compare your effort to the number of waves seen.
Wave Properties 1. Waves are oscillations and they transport energy. The energy of a wave is proportional to its frequency. Fast oscillation = high frequency = high energy Slow oscillation = low frequency = low energy
Wave Amplitude 2. The amplitude is a measure of the wave intensity. SOUND: amplitude corresponds to loudness. LIGHT: amplitude corresponds to brightness.
3. What is the Wavelength? Measure from any identical two successive points (nm) 5 10 15 20 25 30 35 40
What is the Wave length? Measure from any identical two successive points (nm) 5 10 15 20 25 30 35 40 30nm – 10nm = 20nm
What is the Wave length? Measure from any identical two successive points There are 4 complete oscillations depicted here ONE WAVE = 1 COMPLETE OSCILLATION (nm) 5 10 15 20 25 30 35 40 22.5nm - 2.5nm = 20nm
Frequency 4. Frequency = number of WAVES passing a stationary point per second (Hertz)
Frequency and Period 5. Period (T) = length of time for one oscillation T = 1/f f = 1/T
v =λf = (0.25m)(3 Hz) v = 0.75 m/s Wave Speed 6. Wave speed depends on the wavelength and frequency. Formula: v = l f One end of a rope is vibrated to produce a wave with a wavelength of 0.25 meters. The frequency of the wave is 3 Hertz. What is the speed of the wave? v =λf = (0.25m)(3 Hz) v = 0.75 m/s
7. The relationship between frequency and wavelength: Frequency increases Energy increases Wavelength decreases
8. Behavior of Waves -Reflection occurs when a wave bounces off a surface that it cannot pass through. A reflected wave has a smaller amplitude than the original wave because some energy is lost during reflection.
8. Behavior of Waves -Refraction occurs when a wave enters a meduim at an angle and one side of the waves moves more slowly than the other side.
8. Behavior of Waves -Diffraction occurs when a wave bends around an obstacle or passes through an opening.
8. Behavior of Waves -Interference occurs when two or more waves overlap and combine.
9.Constructive Interference Waves combine without any phase difference When they oscillate together (“in phase”) Crest meets Crest
Wave Addition Amplitude ~ Intensity
10. Destructive Interference Waves combine and oscillate “out-of-phase”
Constructive and Destructive Interference
Wave Subtraction
11. Complete the wave speed worksheet individually!