Physics Flashcards
waves
motion of disturbance
mechanical eaves
include sound waves, require a medium
non-mechanical
travel thru a vacuum, light waves etc
pulse wave
singular traveling pulse
periodic wave
repeatedly generated
transverse
wave and particle motion perpendicular
crest
highest point above eq
trough
lowest point below eq
amplitude
max distance from eq (measured from eq to c or t)
longitudinal
wave and particle motion parallel like sound waves
how do waves transfer energy
Waves transfer energy by the vibration of
matter The energy moves while the particles
vibrate locally and the medium remains in
place.
rate of energy transfer
The rate of energy transfer depends on the
amplitude. The greater the amplitude the
more energy the wave carries in a given time
interval.
Wavelength
distance wave travels for one cycle
measure from cr to cr or tr to tr
high density/pressure
crest
low density/pressure
trough
period and frequency
The source of wave motion is a vibrating object
Period is the time it takes for one full wavelength to pass any given point
Frq is the number of wavelengths that pass a given point in second
speed
wavelength/time
Wave interference
is the phenomenon that occurs when two waves meet while traveling along the same medium.
Constructive interference
is a type of interference that occurs at any location along the medium where the two interfering waves have a displacement in the same direction.
Destructive interference
is a type of interference that occurs at any location along the medium where the two interfering waves have a displacement in the opposite direction (noise cancellation)
Reflection at a Boundary: (free end)
Now consider what would happen if the end of the rope were free to move. Instead of being securely attached to a lab pole, suppose it is attached to a ring that is loosely fit around the pole. Because the right end of the rope is no longer secured to the pole, the last particle of the rope will be able to move when a disturbance reaches it. This end of the rope is referred to as a free end.
Reflection at a Boundary: (fixed end)
First consider an elastic rope stretched from end to end. One end will be securely attached to a pole on a lab bench while the other end will be held in the hand in order to introduce pulses into the medium. Because the right end of the rope is attached to a pole (which is attached to a lab bench) (which is attached to the floor that is attached to the building that is attached to the Earth), the last particle of the rope will be unable to move when a disturbance reaches it. This end of the rope is referred to as a fixed end.
resonance
forced vibrations at the same
fr cause an increase in
amplitude
standing waves
a vibration of a system in which some particular points remain fixed while others between them vibrate with the maximum amplitude.
causes:
· Reflections at Two Boundaries (at either end)
· Constructive/Destructive Interference
nodes
complete destructive interference (ends of strings can't vibrate)
antinodes
increased
amplitude midway
between adjacent nodes
distance btwn nodes
half wavelength
fundamental frequency
lowest frequency of standing wave
Harmonics
: integral multiples of the fundamental
frequency.
n
n is called the harmonic number and
is equal to 1, 2, 3 …
closed both ends
v/2L
open both ends
nv/2l
open one end closed other
nv/4l ONLY ODD HARMONIC
Timbre
- sound quality due to the mixture of
harmonics at varying intensities
The first harmonic (fundamental frequency) determines overall pitch;
other harmonics change timbre (overtones)
beats
interference of waves of slightly different frequencies that result in a
sound that alternates between being loud and soft
Number of Beats per Second =
Difference btwn the 2 Frequencies
order of waves
radio, micro,
order of light waves
radio, micro, infra, ultraviolet, x rays, gamma
frq increases, wl decreases
visible light
btwn infra and UV
what are microwaves used for
radar, atomic/molecular research, aircraft nav, microwave ovens
infrared
thermal imaging, photography, pt
gamma rays
exam thick material, radiation therapy treatment, food irradiation
intensity
light bulbs are rated by light input and light output
luminous flux
rate at which light emitted from source
illuminance
luminous flux/area, decreases as u move from light source
light intensity
pitch
perceived highness or lowness of sound
variables affecting speed of sound
closeness of particles (solid, liquid, gas)
temp of particles (increase in t = increase in v)
types of sound waves
infrasonic - under 20 Hz
audible (humans) btwen 20 and 20k
ultrasonic over 20k
doppler effect
increase or decrease in frequency due to source moving
causes change in pitch
sound intensity
amount of energy flowing per unit
perpendicular to the direction in which the sound waves are travelling.
power/area
