Waves and sounds Flashcards
waves in hearing
longitudinal (make long distance calls)
Waves in light
transverse waves
sound waves
need a medium to travel through since it is a change in pressure from high to low
light waves
do not need a medium since they transfer energy through alternating electric and magnetic fields
mechanical waves
obey the laws of classical mechanics and require a medium
electromagnetic waves
do not need a medium to travel through
wavelength
is the distance from any point in the wave to the point where the wave begins to repeat itself
frequency
is the number of wavelengths that pass a fixed point in one second
period
is the time it takes the wave to travel the distance of one wavelength and is the reciprocal of frequency
frequency does not change when
you move from one medium to another and neither does the period
what changes when a wave travels through another medium
the velocity changes
what happens to a sound wave when temperature increases in a gas
sounds waves will move more quickly
Why do sound waves travel faster in water than air
water has a much higher bulk modulus
amplitude of a wave
can be measured as the distance between the x-axis and either the top of a crest or the bottom of a trough
what happens to amplitude when a wave moves from one medium to another
amplitude changes
pitch
a measure of how high or low a note sounds, correlates with frequency
intensity
is the power level of a sound wave.
in decibels if you increase by 100 you add
10
when a wave reflects off a medium that is more dense
it is inverted
when a wave reflects off a medium less dense it is
it is reflected upright
audible frequency for humans
20 to 20,000Hz
waves above the frequency for humans
ultrasonic
for an ultrasound machine the greater the difference in density
the greater the intensity of reflected sound
point created by maximum destructive interference is called
node
two vertical lines experience maximum constructive interference
antinode
attenuation
the decrease in the intensity of a wave propagating through a medium
when a wave attenuates what decreases
its intensity
doppler effect
is the change in the observed frequency when a wave source or observe moves towards or away from each other
when the source or the observer is moving toward each other
the observed frequency is higher
as distance decreases so does the
time interval between wave fronts
what does the wavelength for light do when the source and observer are approaching each other
creates a blue shift
when objects are moving in the same direction at the same speed
there is no doppler effect
shock waves
is a conical wave front produced when the velocity of the sound source exceeds the velocity of the sound wave
pressures differences in a shock wave are
so different that it causes the observer to perceive it as a boom
amplitude of a standing wave is
constant
Intensity and amplitude related
I= A^2
30 db to 10 db is a
100 fold decrease
light acts like both
a wave and a particle
emission of light occurs when
the light emitted transitions from higher to lower energy states
light emitted by electrons is in the form of
photons
the dominant frequency of emitted light is
directly proportional to the temperature
black is the absorption of
all light
white is the reflection of
all visible light
when light is polarized
its electric and magnetic fields are oriented in a particular rather than a random way
if light oscillates parallel to the y-axis
it is said to be vertically polarized
if light oscillates parallel to the x-axis
it is said to be horizontally polarized
magnetic fields oscillate in planes perpendicular to the
planes in which electric fields oscillate
source of light is
a vibrating charge
light is said to be circularly polarized when it consists of electric fields of
constant magnitude that change direction in a rotary manner
reflection is
light bouncing off the boundary between media
Refraction
is light bending as it passes into a new medium
Dispersion
is a type of refraction is the splitting of light according to frequency
Diffraction is
the spreading of light when it encounters an edge
The angle at which a wave strikes an interface is called
the angle of incidence
the angle at which a wave is reflected is called
the angle of reflection
the angle of incidence is equal to the angle of reflection when light
reflects off a flat surface
what do all waves do
refract
the greater index of refraction results in
the more slowly light moves through the medium
indice of refraction for water
1.3
indice of refraction for glass
1.5
when light approaches a medium with a higher index of refraction at an angle other than 90 degrees
one part of the wave front changes speed before the other and the light ray remains perpendicular to the wave fronts
when light enters a new medium what remains the same and what changes
the frequency remains the same while the wavelength and velocity change
refraction does not change the
phase of the wave at the interface between two media
if the medium’s index of refraction is higher
the wavelength becomes shorter
if the index of refraction is lower
the wavelength becomes longer
when light is coming from a higher index of refraction the angle of incidence can be so great to cause
total internal reflection
if the angle of incidence is large enough
all photons will be reflected at the angle of reflection and none will refract. angle called critical angle
critical angle equation
theta critical= sin inverse (n2/n1)
dispersion
is the separation of light into different frequencies due to their different indices of refraction in a medium
chromatic dispersion
has light refracted at its different frequencies resulting in different velocities and wavelengths
diffraction is
the spreading of light that occurs when a wave bends around the edges of an object or opening
longer wavelengths will do what compared to shorter wavelengths
defract more
the fact that a wave can be reflected supports both
the particle theory of light and the wave theory
the difference between lens and mirrors with interaction with light
light reflects when it encounters a mirror and refracts when it encounters a lens
thin lens
is a lens whose maximal thickness is small relative to the radius of curvature, object distance, and image distance
focal point
the point at which parallel light rays converge or appear to converge after reflecting off of the mirror or passing through the lens
real focal point
where light rays actually converge
virtual focal point
is a point at which light only appears to converge
focal point for a concave mirror
lies in front of the mirror
focal point for a convex mirror
is located behind the mirror
focal length
is the distance between a mirror and its focal point. It is equal to half the radius of curvature f=R/2
power of a lens is determined by
P=1/f
lens have two
focal points
what is the power of a lens measured in
diopters (m^-1) must convert into meters to calculate
converging mirror
reflects light rays such that they converge at a point in front of the mirror. The point at which reflected rays converge is the focal point
Converging lens
light converges behind where the light source is
converging mirror
concave
converging lens
convex
what makes a spherical mirror reflect light at one point
if the radius of curvature is large and the angles of incidence are relatively small
how does a diverging mirror reflect light
reflects light rays such that the observer perceives them as converging at a point on the opposite side of the mirror from the observer
diverging lens
refracts light rays such that they appear to converge at a point on the same side of the lens as the light source, opposite the side of the observer
diverging mirror is a
convex mirror
diverging lens is a
concave lens
if the center of a lens is thicker than its ends
it will converge light regardless of its shape or which direction light moves through the lens
real, inverted image
on the same side of the mirror or lens as the observer and positive
virtual, upright
on the opposite side of the mirror or lens from the observer and negative
positive and negative are dictated by
positive on the same as the observer and negative on the opposite side of the observer
diverging lens and mirrors always produce
virtual upright images
what is unique about convergers
they can make both real,inverted images and virtual upright images
when the object is located beyond the focal point
convergers will always produce a real inverted image located on the side of the observer
if the object is placed within the focal length the image formed will be (convergers)
virtual and upright
real image is always located
on the same side as the observer
focal distance for a converging mirror and lens
positive
focal distance for a diverging mirror and lens
negative
object distances are given a positive sign when
objects are where they belong. objects belong on the same side as the observer for mirrors and on the opposite side from an observer for lenses
magnification
-di/do
diverging lens and mirrors always form images that are
smaller in size than the objects they represent
plane mirrors
the image formed by a plane mirror is the same distance from the mirror as the object
chromatic abberation
arise when light of higher frequencies focuses closer to a lens than does light of lower frequencies
chromatic abberations only occur when
different frequencies of light pass through a lens simultaneously
spherical abberations
when rays farther from the center of a lens focus at different points than do rays closer to the center of the lens
the lateral magnification of a two lens system is the product of
the lateral magnifications of each lens M=m1*m2
Two lenses in contact with each other have an effective power equal to the sum of their individual powers
Peff=P1+P2
increase bending of light would increase
the lens power
