Waves
Wave : a disturbance that moves energy through space 1) the material that gets disturbed is the Medium 2) the medium does not travel through space it just bounces up and down or back and forth in place
2 Types of Waves 1) Transverse: medium motion perpendicular to direction of wave (energy) travel
2) Longitudinal: motion of medium is parallel to wave direction Medium bunches up into compressions and spreads out into rarefactions
Amplitude : max distance molecules displaced from rest position Greater amplitude = more energy = louder sound (more sound intensity) = brighter light (more intense light)
Wavelength(ג) – distance between 2 consecutive rarefactions or compressions (crests or troughs)
Wavelength Determines type of electromagnetic wave * radio wave vs visible light vs X-ray * color of light
Frequency: # waves per second How many waves pass a set point per second 1 wave/sec = 1 hertz At set speed frequency = wavelength So frequency of light also determines color Frequency of sound = pitch High frequency = high pitch Ultrasonic – higher pitch 20 Hz – 20,000 Hz = audible sound subsonic – lower pitch
Period = time for 1 wave to pass set point Period = 1/frequency
Wave speed = how fast one crest is moving Speed = frequency X wavelengths Speed of light waves in a vacuum is constant Light slows slightly if moving through a medium Different mediums conduct waves at different speeds
1. Waves are reflected when they bounce back from an object Angle of incidence = between incident wave and normal (normal = line perpendicular to object) Angle of reflection = between normal and reflected wave
Law of Reflection Angle of reflection = angle of incidence
Diffuse reflection = many directions, rough surface, fig. 15.5 p 256, less glare dry road
2. Refraction – wave bends due to a change in speed 2. Refraction – wave bends due to a change in speed. Often as wave moves from 1 medium to another. (Water, air) 3. Diffraction – bending of waves around a barrier (p274)
4) Interference = 2 waves combine to form a new wave a. Constructive = crests overlap to create larger amplitude b. Destructive = crest lines up with trough to cancel
Interference Constructive Destructive