physics notes set 2
TRANSCRIPT
-
8/3/2019 Physics Notes Set 2
1/12
1
Fluids
substances that can flow and can easily change in shape usually are liquids and gases
Fluid Mechanics
Fluid Statics
study of fluids at rest
Fluid Dynamics
study of fluids inmotion
Density Pressure BuoyancySurfaceTension
Bernoullis PrincipleArchimedes
PrinciplePascalsPrinciple
Density
ratio of mass of a substance to its
volume independent to the amount present in a
substance
(rho)
Pressure force per unit area P Kinds of pressure
hydrostatic pressure exerted on an object by a column of liquid
air/atmospheric pressure exerted on an object by air
A barometer is an instrument used to measure pressure. It was invented byEvangelista Torricelli.
Pascals principle (by Blaise Pascal) states that for any change in pressureapplied at any given point on a confined fluid is transmitted undiminishedthroughout the fluid
Buoyancy is the apparent loss of weight of objects when submerged in aliquid
Buoyant force () is the upward force exerted by water that seems tobalance the force of gravity
Archimedes principle states that a body partly or entirely submerged in afluid is buoyed up by a force equal in magnitude to the weight of the displacedfluid
-
8/3/2019 Physics Notes Set 2
2/12
-
8/3/2019 Physics Notes Set 2
3/12
3
Scale Interval ProponentH2O
BoilsH2O
FreezesConversion
Celsius 100AndersCelsius 100C 0C
()
Fahrenheit 180DanielGabriel
Fahrenheit212F 32F
Kelvin 100 Lord Kelvin 373K 273K Linear Thermal Expansion wherein: is the length of an object, is the linear thermal expansion coefficient ( or ) is the temperature in Kelvin or degrees Celsius
Volume Thermal Expansion wherein: is the length of an object, is the volume thermal expansion coefficient ( or ), and is the temperature in Kelvin or degrees Celsius
Three modes of heat transfer:1] Conduction direct contact
conductors are materials that conduct heat well; has loosely-boundelectrons
insulators are materials that delay heat transfer2] Convection currents in the fluid3] Radiation through electromagnetic waves
hotter objects emit shorter wavelengths while colder objects emit longerwavelengths
Specific heat capacity is the amount of heat needed to change thetemperature of a quantity by 1C
wherein:
is change in temperature, is the specific heat capacity constant, is the mass of the object, and is change in heatThe SI unit of specific heat capacity is
or ()Latent heat is the amount of energy/heat given out / absorbed when a
substance changes phase which do not change in temperature
Latent heat of fusion () is the amount of heat that must be added to asubstance at its melting point to change from solid to liquid Latent heat of vaporization () is the amount of heat that must be added to a
substance at its boiling point to change from solid to liquid
-
8/3/2019 Physics Notes Set 2
4/12
4
History of Wave and Harmonics
19th
century BC birth of acoustics and optics
14th
century BC the interest in musical instruments prompted the mathematical
study of vibrating bodies and of the propagation of sound throughair
4th
century BC Pythagoras established the connection between musical soundsand mathematics
Robert Hooke and Christian Huygens believed light to be a form of wavemotion
Thomas Young (1800) firmly established the wave nature of light Heinrich Hertz (1886) established that radio waves were of the nature of light
waves
AM radio waves are measured in kHz while FM radio waves are measuredin MHz
20th century wave concepts were used to develop the theory of quantummechanics called wave mechanics
Vibration is the periodic or repeated motion of a particle or mechanicalsystem.
Simple harmonic motion is the back-and-forth vibratory motion of a swingingpendulum wherein the restoring force is proportional to the displacement from theequilibrium.
Hookes Law:
wherein: is the spring constant; and is the change of length of the spring
Types of waves:1] According to the medium requirement:
A] Mechanical waves waves that require a medium (water waves, soundwaves, waves that move along a rope or a string)
B] Electromagnetic waves waves that does not require a medium2] According to the number of travelling pulse:
A] Pulse waves single travelling pulseB] Periodic wave continuous generation of pulses3] According to the direction of motion
A] Transverse wave have vibrations that are at a right angle or perpendicularto the direction of the wave
B] Longitudinal wave have vibrations that are along the direction of the waveC]Surface wave is a combination of both transverse and longitudinal waves.
Measure of awave
Description FormulaSI
Unit
wavelength ()
distance between two consecutive
crests or troughs m
period (T) time to complete one cycle
s
frequency (f)the number of complete waves orcycles per unit time
Hz
-
8/3/2019 Physics Notes Set 2
5/12
5
amplitudethe displacement from the midpoint tothe crest/trough of the wave
m
wave speed (v)depends on the medium through whichthe wave moves
m s
wave energy (E)energy carried by the wave isproportional to the frequency of thewave
1 W
Characteristics of a Sound Wave:
we cannot see sound waves, but we can measure all their properties
composed of waves of compression and rarefaction (a sound wave is a
longitudinal wave) follows an orderly pattern
carries energy
Sound is produced when vibration causes pressure variations in the medium.
Propagation of sound:
travel through solids, liquids and gases but not in vacuum travel more efficiently in denser materials
propagates three-dimensionally (all directions)
approximately spherical
The human ear is an amazing sound detector
OuterEar
Three TinyBones:Anvil,
Hammer,Stirrup
Cochlea Auditory
Nerve Brain
Physical properties of sound waves:
1] Pitch perception of highness or lowness of sound depends on the frequency of sound waveA] audio frequency range: 20Hz 20 000HzB] ultrasonics: above 20 000HzC] infrasonics: below 20Hz Doppler Effect (Christian Doppler) is the change in frequency or pitch of a
sound that is caused by the movement of either the source, the listener, orboth blue shift is the increase in frequency due to the Doppler effect while the
red shift is the decrease in frequency due to the Doppler effect2] Loudness
sound level or intensity
determined mainly by the amplitude of the sound wave the threshold of hearing is 0dB while the threshold of pain is 120dB
1is the Plancks constant ()
-
8/3/2019 Physics Notes Set 2
6/12
6
the second sound is noticeably louder than the first sound if the secondsound is 1dB higher than the first sound;the second sound is twice as loud as the first sound if the second sound is
10dB higher than the first sound;two equal sound levels combined will create a sound that is 3dB higher thantheir original volume
3] Timbre tone color or tone quality
distinguish between two different sounds that have the same pitch andloudness
depends on the wave form of the sound wave
different wave forms creates different tone quality
Speed of sound doesnt depend on the source but on the medium through
which they move. It is dependent on the following:1] density since sound waves move well through dense materials because
their molecules are close together2] elasticity since sound waves move fast through elastic materials3] temperature since sound waves travel faster through warm air than through
cold air
has less effect on solids or liquids at 0C the speed of sound in gas is estimated to be about m s speed increases by about m s for every increase in temperature a supersonic boom will occur if a source moving at speeds greater than
the speed of sound that would cause the waves to pile up
Sound wave characteristics:1] Reflection
bouncing of wave an echo is any reflected sound heard shortly after the original sound
affected by two factors:A] properties of the reflecting sound since greater energy is reflected if the
surface is hard and smoothB] distance of the reflecting surface from the source since to hear an echo,
the sound source must be at least 17m away from the reflecting surface
2] Refraction sound waves bend or refract as they move through air (differences in air
densities)3] Diffraction
bending of sound waves due to a barrier or opening
greatest in high pitch sounds and less in low pitch4] Interference has two types:
Constructive Interference occurs when two waves combine with eachother and create another wave of higher intensity
Destructive Interference occurs when two waves combine with each other
and create another wave of lower intensity
Music vs Noise
pleasing combination of tones
regular pattern rhythm, harmony, melody, pitch, quality
random and irregular
unwanted sound
-
8/3/2019 Physics Notes Set 2
7/12
7
Musical Instruments
String Instruments
produce tone when strings vibrate
higher vibration yields higher volume long and thick strings produce low pitch sounds while short and thin strings
produce high pitch sounds Wind Instruments
contain a column of air that vibrates when air is blown a long air column will produce a low pitch sound while a short air column will
produce a high pitch sound Percussion Instruments
produce sound when they are struck depends on how hard one strikes the instrument
pitch is affected by the tension on the drum covering
-
8/3/2019 Physics Notes Set 2
8/12
8
Optics is the study of light
Nature of Light
light does spread out (ChristianHuygens on his Wave Theory ofLight)
light travels only in a straight line(Isaac Newton on hisCorpuscular Theory)
discovered the diffraction and interference of light which can be explained onlyin terms of wave theory (Thomas Young, 1801)
predicted that changing electric and magnetic fields can propagate throughspace as electromagnetic waves and light itself is an electromagnetic wave(James Clerk Maxwell, 1860)
discovered the existence of electromagnetic waves through radio wavesshared same property of light (Heinrich Hertz, 1880)
proposed that energy comes in discrete units called quanta (Max Planck,1900)
theorized that light is composed of bundles of wave energy called photons(Albert Einstein, 1905, on his Photoelectric Effect)
shared that photons of X-rays decreased in energy when colliding withelectrons (Arthur Compton, 1923)
light has a dual nature; behaves as both wave and particle (Louis Victor deBroglie, 1924)
Producing Visible Light
an illuminated object is an object that reflects light waves a luminous object is an object that gives off its own light
Two Ways to Produce Light incandescence
light is produced when the atoms of an object are heated
emitted nearly all extremely hot objects when temperature is lower, the wavelength is higher which will produce a
reddish color; conversely, when temperature is higher, the wavelength is
lower which will produce a bluish color luminance
only electrons of the atom are involved
no need for large amount of heat caused by the movement of electrons from higher to lower energy levela] Chemiluminescence
production of light as a result of chemical reactionb] Bioluminescence
production of light by organismsc] Fluorescence
production of light when excited by another source of radiation light ceases when external excitation stops
d] Phosphorescence
production of light when excited by another source of radiation luminescence persists even after the removal of the external excitation
Wave Particle
Christian Huygens Isaac NewtonThomas Young Max PlanckJames Clerk Maxwell Arthur Compton
Heinrich HertzAlbert Einstein
-
8/3/2019 Physics Notes Set 2
9/12
9
Formation of Shadow
shadow formation is a proof that
light travels in a straight line size of shadow depends on the
distance of the point source andthe size of light source
The Speed of Light (c) is equal to Person Experiment Value
Galileo Galilei lantern experimentOlaus Roener studied the period of Io
Christian Huygens refined Roeners data Armand Hippolyte
Louis Fizean toothed wheel Jean Bernard LeonFoucalt
rotating mirror Albert Michelson octagonal mirror
Photometry is the measurement of the properties of lightLuminousIntensity
brightness of lightcandela
(cd)
LuminousFlux
(LuminousPower)
rate at which light is emitted from asource and strikes the surface of a
whole sphere
lumen
(lm)
Illuminance measures the amount of illumination lux (lx)
LuminousEfficiency
ratio of light flux emitted by thesource to the power supplied to thesource
Types of Materials
opaque materials absorb light waves that fall on them; absorb light without re-emission
translucent materials allow light to be transmitted through them but its raysare distorted during the passage
transparent materials transmit light waves and permit objects to be seenclearly through them; produce a chain of absorption and re-emission of light
Light Wave Interactions
reflection is the bouncing off of light waves diffraction is a kind of reflection wherein light strikes a rough, uneven
surface regular/specular reflection is a kind of reflection wherein light strikes a
smooth, flat surface refraction is the bending of light waves due to difference in density
law of refraction (Snells Law)
(index of refraction)
Ionized GasesColor Gas
red light Pure Neongreenish blue light Argon and Mercurygolden yellow light Helium
pure violet light Krypton
-
8/3/2019 Physics Notes Set 2
10/12
10
total internal reflection occurs when light travels from a denser to lessdense medium and strikes the surface at an angle greater from the criticalangle, the light beam is not able to get out of the denser material
dispersion is the process by what light is separated into its colors due todifferences in degrees of refraction interference (Thomas Young on his Double Slit Experiment)
diffraction is the bending of light waves due to a barrier or opening Huygens Principle states that every point on any wave front of light from a
point source may be regarded as a new point source of secondary waves polarization occurs to a light wave if its vibrations are confined to a single
place a polarizer transmits only the wave that vibrates parallel to the alignment of
the crystals in it an analyzer transmits only the wave that vibrates perpendicularly to the first
polarized sheet
Colors
Isaac Newton made a systematic study of colors using his prism-spectrumexperiment
an object can reflect only light of frequency present in the illuminating light
Color Mixing
color mixing by addition mixing colored lights of different frequencies
white light has three regions, primary addition colors, which are red,green, and blue
color mixing by subtraction mixing pigments which absorb different frequencies of light
three regions, primary subtraction colors, which are magenta, cyan,and yellow
Mirrors
Plane Mirrors
flat surface Curved/Spherical Mirrors
Convex
curves outward diverging mirror
Concave
curves inward like a cave converging mirror
Parts of a curved mirrorVertex V
Center of
Curvature C center of the sphere from which the mirror is formedFocal Point F midpoint of C and VRadius ofCurvature
R distance from C to V
Focal Length Fdistance from F to V
Pigment Absorbs Reflects
R B G RG B R GB R G BY R R GC G G BM B B R
-
8/3/2019 Physics Notes Set 2
11/12
11
Principal Axis PAline passing through C, F, and Vtangent to the curve of the vertex and perpendicularto the mirror
Parameters of mirrors
type (virtual/real) orientation (inverted/upright or erect) position (between/at point/beyond) size (smaller/larger/same size)
Ray Diagram
a ray parallel to the PA is reflected through the focal point, F a ray passing through the focal point, F, is reflected parallel to the PA a ray passing through the center of curvature, C, is reflected back along its
own path
The TOPS parameter of a concave mirrorLocation F ~ C C ~ F ~ V @ C @ F @
Type Real Real virtual real no image realOrientation Inverted Inverted upright inverted no image ???
Position C ~ F ~ C behind @ C no image FSize Larger Smaller larger same no image no image
Lenses are curved pieces of glass or some other transparent materials that are
used to refract light convex (converging) lens
thicker at the center than at the edges has six TOPS cases (see below)
concave (diverging) lens
thinner at the center than at the edges has only one TOPS case:
T virtualO uprightP ???S smaller
The TOPS parameter of a convex lensLocation F ~ C C ~ F ~ O @ C @ F @
Type Real Real virtual real no image realOrientation Inverted Inverted upright inverted no image ???
Position C ~ F ~ C F ~ O @ C no image FSize Larger Smaller larger same no image no image
-
8/3/2019 Physics Notes Set 2
12/12
12
Mirror/Thin Lens Equation:
wherein is the focal length,
is the distance of the object and is the distance of the image.Magnification Equation:
wherein is the magnification, is the distance of the object, is the distance of the image, is the height ofthe object and is the height of the image.