Reflections and Rarefactions Flashcards
reflection
the wave bounces off the new medium
transmission
the wave starts moving through the new medium
absorption
the wave’s energy is absorbed by the new medium as heat
what are wave fronts
lines that correspond to the crests of the wave
waves are represented using wavefronts
what are rays
they represent waves in the form of arrows.
the are drawn perpendicular to the wavefronts in the direction the wave is moving.
what is the reflected ray
represents the wave after it is reflected by the surface. leaves the surface from the same point
what is the incident ray
represent the wave that approaches the surface.
meets the surface at the base of the normal
what is the angle of incidence
angle between normal and incident ray
what is the angle of reflection
is the angle between the reflected ray and the normal
law of reflection
angle of incidence = angle of reflection
what is reverberation
when this time interval is shorter than 0.1 seconds, your brain interprets the waves as a single sound.
excessive reverberation make it hard to comprehend
what is an echo
when a reflected wave reaches your ears more than 0.1 seconds after you hear the original, you can hear the reflected sound as an echo.
what does the speed of the sound waves depend on
if there is a smaller distance between the particles in the medium sound waves travel faster
at higher temperatures, particles move faster and can transfer energy quicker.
what happens when a wave moves from one medium to another and its velocity changes
- its frequency remains constant
- wavelength changes
- if the wave enters the new medium at an angle, it refracts
why do wavefronts refract
the part of the wavefront that reaches the boundary first slows down or speeds up, while the remainder of the wavefront still in the original medium continues at original speed.
refraction of sound waves entering a denser or hotter medium
velocity and wavelength increase and the wave bends away from the normal (angle of refraction is bigger than angle of incidence)
refraction of sounds waves entering a less dense and cooler medium
velocity and wavelength decreases
- wave bends towards the normal (angle of incidence is greater than angle of refraction)
what is the critical angle
eventually the angle of refraction reaches 90 degrees from the noral and the wave travels along the boundary between the two mediums. this is the angle of incidence is called the critical angle
what is total internal reflection
when angle of incidence is bigger than critical angle, refraction doesnt occur anymore and the wave is entirely reflected and does not enter the other medium.
how is refraction of sound used in real life
sound waves reflect back and forth along the inner walls of a tube in a stethoscope and carries sound
total internal reflection protects marine life from most sound produced by wind turbines
snells law
sin (angle of reflection)/sin (angle of incidence)
velocity of reflection/velocity of incidence
=
wavelength of reflection/wavelength of incidence
