Midterm 4: Waves and Mirrors Flashcards
Wave
a traveling disturbance that transmits energy (travels through a medium)
pulse
a single disturbance
periodic wave
regular repeating disturbance
what are the 4 types of waves
longitudinal, transverse, mechanical, and electromagnetic (EM)
longitudinal wave
the vibrating disturbance is parallel to the direction of travel of the wave
exs of longitudinal wave
sound, seismic wave (p-wave)
transverse wave
vibration is at right angles to the direction of travel of the wave
exs of transverse wave
electromagnetic (EM) wave, seismic wave (s-wave), wave on a rope/spring
mechanical wave
requires a medium to travel through
exs of mechanical wave
sound, seismic
medium
the matter through which a wave travels
electromagnetic (EM) wave
don’t require a medium to travel through
exs of electromagnetic (EM) wave
light, x-rays, radio
sound
longitudinal compression waves
visible light
transverse wave
frequency(f)
of disturbances per second
what are the units of frequency
hertz
what are the units of period
seconds
period (T)
the time it takes for one wave to pass by a given point
amplitude (A)
max. vertical displacement from rest position.
what determines the energy of a wave
amplitude
crest (peak)
the highest point above the equilibrium position
trough
the lowest point below the equilibrium position
wavelength(λ)
the distance from crest to crest or from trough to trough
what are the units for wavelength
meter (m)
what is the property of velocity
the direction of the velocity of a wave is always the same as the direction of propagation of the wave
phase
points on a wave with the same displacement from the baseline and velocity
in phase
when peaks of one wave align with the peaks of the others
out of phase
when peaks of one wave align with the troughs of the other
refraction
the change in the characteristics of a wave when it goes from one medium to another
properties that change for refraction
wavelength, velocity, direction, and amplitude
properties that stay the same for refraction
frequency and period
in the new medium, what happens if the wave travels faster
wavelength increases
in the new medium, what happens if the wave travels slower
wavelength decreases
what does the degree to which the properties of a wave change when it passes from one medium to another depend on
relative speed of the wave in the two media
index of refraction and formula
For light waves, the ratio of the speed of light in a vacuum to the speed of light in the medium
n= c/v
the index of refraction is always greater than or equal to?
1
Snell’s law (aka law of refraction) and formula
describes the relationship between the angles of incidence and refraction when a wave passes through a boundary between two different media
n1 sin(theta 1) = n2 sin (theta 2)
reflection
occurs when a wave bounces off the boundary btw. 2 media
what changes when reflection occurs?
amplitude and direction
what happens to pulse during a reflection off a fixed end
pulse is inverted when it’s reflected
what happens to pulse during a reflection off a loose end
pulse isn’t inverted
diffraction
bending of a wave as it moves around an obstacle or passes through a narrow opening
what changes during a diffraction
direction (edge of the obstacle bends the wave)
what affects the amount of diffraction?
- wavelength/frequency of wave (lower frequency(longer wavelength)=more diffraction 2. size of the opening/obstacle (smaller opening=more diffraction)
what would produce more diffraction
greater diff. btw. size of opening and wavelength
true or false: waves travel through each other or occupy the same space at the same time
true
interference
addition (superposition) of two or more waves that results in a new wave pattern
Constructive Interference
occurs when the interfering waves are in phase; pulses add together to form a pulse with greater amplitude
Destructive Interference
occurs when the interfering waves are out of phase; pulses subtract from each to form a pulse with smaller amplitude
Standing waves (aka stationary waves)
waves that remain in a constant position
when are standing waves produced
whenever two waves of identical frequency traveling opposite directions along the same medium interfere with one another
exs of standing wave
a musical note vibrating a guitar string, or the air inside a flute
what are standing wave patterns characterized by
nodes and antinodes
nodes
certain fixed points along the medium which undergo no displacement
antinodes
points of maximum oscillations
resonance
When the frequency of the standing wave matches the natural frequency of the object that it’s vibrating
what effect does resonance have on the standing wave
causes the standing wave to be amplified
conditions for resonance
case 1: - Both ends of the medium are nodes or both ends are anti-nodes (ex: guitar string, or a pipe open at both ends) - In order for resonance to occur, the length of the medium must be an integer multiple of half wavelength of the wave case 2: - One end of the medium is a node and the other is an ant-node (ex: a pipe closed at one end) - In order for resonance to occur, the length of the medium must be an odd integer multiple of one quarter wavelength of the wave
how many number of frequencies can resonate in one medium
an infinite number
fundamental frequency (f1)
the lowest possible frequency aka 1st harmonic
harmonic series
The set of higher frequencies that can resonate on a given medium
doppler effect
the change in the apparent frequency of a wave as the observer and the source of the wave move towards or away from each other
ex. of doppler effect
the apparent change in the frequency of a moving ambulance siren; a shift in the color of light seen from distant starts moving away from the earth
properties of a source moving towards you
higher frequency and shorter wavelength
properties of a source moving away from you
lower frequency and longer wavelength
incident ray
ray as it approaches the reflective surface
reflected ray
incident ray hits the surface, bounces off at the same angle.
light is a?
wave that can be reflected
how does light travel
in a straight line
law of reflection
when a ray reflects off a surface, the angle of incidence is equal to the angle of reflection
specular reflection
reflection off flat, smooth surfaces such as mirrors or water, where light from a single incoming direction (ray) is reflected into a single outgoing direction. AKA parallel incident rays produce parallel reflected rays
diffuse reflection
reflection off of a non-smooth surface such as the cover of a book where rays reflect in various direction. AKA parallel incident rays produce reflected rays in diff. directions.
where do images occur in a plane mirror?
at the intersection of reflected rays
draw the fundamental frequency and harmonics for both cases of resonance.
convergent rays
When the rays of light coming from different directions meet at a point
divergent rays
When the rays of light starting from a point travel in different directions
describe the image formed by a plane mirror
behind the mirror, the same size as the object, virtual (unreal), same distance from the mirror as the object, laterally inverted(sideways reversal of left and right)
what does the mirror length need to be in order to see your full image?
1/2 your height
what is a concave spherical mirror also referred to as and what is a convex spherical mirror also referred to as ?
a converging mirror; a diverging mirror
convex spherical mirror
a curved mirror in which the reflective surface bulges toward the light source. Convex mirrors reflect light outwards, therefore they are not used to focus light. Such mirrors always form a virtual image, since the focal point (F) and the centre of curvature (2F) are both imaginary points “inside” the mirror, that cannot be reached. As a result, images formed by these mirrors cannot be projected on a screen, since the image is inside the mirror. The image is smaller than the object, but gets larger as the object approaches the mirror.
when are object and image distances positive/negative?
positive when they form on the front side of the mirror and negative when they form on the back side of the mirror
center of curvature
center of the spherical shell of which the mirror is a small part
represented by C
radius of curvature
distance from the mirror’s surface and the center of curvature
represented by R
object distance
distance between the object and the mirror
represented by P or d(sub o)
image distance
distance between the image and the object
represented by q or d(sub i)
focal length
half of the radius of curvature
represented by f
principal axis
perpendicular to the surface and divides the mirror in half (goes through the center of curvature)
ray diagram
a drawing used to locate an image formed by a mirror
for spherical mirrors, how many kind of reference rays are there and what are they?
3
- incident ray is parallel to the principal axis and the reflected ray goes through the focal length (f)
- incident ray goes through the focal point (f) and the reflected ray is parallel to the principal axis
- incident ray goes through the center of curvature (c) and the reflected ray goes back through the center of curvature
for spherical mirrors, how do you locate the image?
the intersection of any 2 rays
mirror equation
1/object distance + 1/image distance = 1/focal length
magnification equation
M= image height/object heigt = -image distance/object distance
concave spherical mirror or converging spherical mirror
has a reflecting surface that bulges inward (away from the incident light). Concave mirrors reflect light inward to one focal point. They are used to focus light. Unlike convex mirrors, concave mirrors show different image types depending on the distance between the object and the mirror.
These mirrors are called “converging mirrors” because they tend to collect light that falls on them, refocusing parallel incoming rays toward a focus. This is because the light is reflected at different angles, since the normal to the surface differs with each spot on the mirror.
what are the 5 cases for concave mirrors?
- object is located beyond c: image is inverted, reduced, real, and between c and f
- object located at c: image is real, inverted, same size, and is at the center of curvature
- object is between c & f: image is real, inverted, larger, and beyond the center of curvature
- object is located at f: no image is formed
- object is located in front of the mirror: image is upright, magnified, behind the mirror, and virtual
what are the properties of a convex spherical mirror?
the image distance is negative, virtual, upright, focal length is negative, focal point and center of curvature are behind the mirror’s surface, magnification is always less than 1
Sign Conventions for Magnification?
how are reflection and refraction different?
unlike reflection, refraction depends on the media through which the light rays are traveling.
velocity formula for waves
v = (d/t) = (wavelength/T) = wavelength x f
rarefaction
regions where the air particles are spread apart( low air pressure)
compression
regions in the air where the air particles are compressed together (high air pressure)
doppler affect formula
