PHYSICS FINAL REVIEW Flashcards
M, k, d, c, m, u, n, p prefixes
Mega, kilo, deci, centi, milli, micro, nano, pico
10^6, 10^3, 10^-1, 10^-2, 10^-3, 10^-6, 10^-9, 10^-12
Sin 0, 30, 45, 60, 90
Sin 0 = 0 Sin 30 = .5 Sin 45 = .7 Sin 60 = .9 Sin 90 = 1
Cos 0, 30, 45, 60, 90
Cos 0 = 1 Cos 30 = .9 Cos 45 = . 7 Cos 60 = .5 Cos 90 = .0
Tan 0, 30, 45, 60, 90
Tan 0 = 0 Tan 30 = .5 Tan 45 = 1 Tan 60 = 2 Tan 90 = undefined
velocity equation
average velocity ⊽= Δx/Δt
Δx = displacement, Δt = change in time
does not account for distance traveled
speed equation
average speed: v= distance/time
accounts for distance traveled
velocity vs speed
speed is a scalar quality, the rate at which an object covers distance; velocity is a vector quality, and the rate at which the position changes
Gravitational force equation
F = GMm / r^2
G= gravitational constant, M= mass 1, m= mass 2, r=distance between center of mass
pay attention to the relationship between r and force
as r doubles, force is divided by four
SI Units
Density Force Pressure Temperature Energy Power Charge Potential Current Resistance Magnetic Field
Density = kg/m^3 Force = N Pressure = Pa Temperature = K Energy = J Power = W Charge = C Potential = V Current = A Resistance = Ohm Magnetic field = Tesla
static friction and kinetic friction equations and application
static friction: fS MAX = ukN
stationary objects
- can experience the minimum static force (0) if the object is resting on a surface with no applied force
- when static friction is overwhelmed the object will move
kinetic friction: fK = ukN sliding objects (sleds, not tires)
Weight equation
Fg (weight) = mg
Acceleration equation
average acceleration
Δv/Δt
- change in velocity over time
- the value of speed/velocity, distance/displacement are interchangeable in this case
Newton’s first law equation
FNET = ma = 0
A body will remain in its motion unless a net force acts upon it
law of inertia
Newton’s second law equation
FNET = ma
Force is equal to change in momentum per change in time
Newton’s third law equation
FAB = -FBA
For every action there is an equal and opposite reaction
Linear motion equations (velocity, displacement, acceleration, and time)
V = V0 + at
final velocity = initial velocity + acceleration*time
x = V0t + 1/2at^2 displacement = initial velocity(time) + 1/2acceleration*time^2
v^2 = v0^2 + 2ax velocity^2 = initial velocity^2 + 2ax
x = vt displacement = average velocity * time
How to analyze projectile motion
analyze the vertical and horizontal values separately
vy will change at the rate of gravity as acceleration
vx will not change
Inclined planes, Force of gravity parallel to plane and perpendicular to plane
Fg (parallel to plane) = mgsinፀ
Fg (perpendicular to plane) = mgcosፀ
Circular motion equation
Fc= mv^2/r
centripetal force = mass * velocity^2 / radius
acceleration is therefore v^2/r
How to draw free body diagrams
make sure to draw for any calculation on forces
What is translational equilibrium
when the vector sum of all the forces acting on an object is zero
constant speed and constant direction, zero acceleration
What is rotational equilibrium
when the vector sum of all the torques acting on an object is zero
constant angular velocity (probably zero)
Equation for kinetic energy
K = ½ mv^2
units of Joules (like all energy)
Equation for gravitational potential energy
U= mgh
Equation for elastic potential energy
U=1/2kx^2
x is the magnitude of displacement from equilibrium
Equation for total mechanical energy
E = U + K
- energy is never created or destroyed, merely transformed
- this equation does not account for thermal energy so E can decrease
What are the conservative forces and what does that mean
Conservative forces are those that are path independent and that do not dissipate energy, △E = △U + △K = 0
Gravitational, Electrostatic, and Elastic
If the change in energy around any round-trip path is zero, or if the change in energy is equal despite taking any path between two points, then the force is conservative
What are nonconservative forces
Nonconservative forces are when total mechanical energy is not conserved
Wnonconservative = △E = △U + △K
Wnonconservative is the work done by the nonconservative forces only
Work equation for displacement vectors
Work is a form of energy. The transfer of energy by work or heat is the only way by which anything occurs
W = Fdcosθ
θ is the angle between the applied force vector and the displacement vector
Work equation for change in volume with constant pressure
Work is a form of energy. The transfer of energy by work or heat is the only way by which anything occurs
W = P△V for change in volume with constant pressure
if volume stays constant no work is done
Power equation
P = W/t = △E/t
unit is the watt, which is a J/s
Work equation for energy change
Work-energy theorem
Work equals change in kinetic energy
Wnet = △K = KEf - KEi
Mechanical advantage
Mechanical advantage = Forceout/Forcein
deals with forces
Efficiency equation
Efficiency = Workout/Workin
deals with work
=load(load distance) / effort(effort distance)
Zeroth law of thermodynamics
if A is in thermal equilibrium with B and C is in thermal equilibrium with C, A is in thermal equilibrium with C
Converting between temperature equation
F = 9/5C + 32
heat vs temperature
heat is the transfer of thermal energy between systems as a result of different temperatures
thermal expansion equations for length and volume
△L = αL△T
Change in length = (coefficient of thermal expansion)(Original length)(Temperature change in Celsius)
for liquids: △V = βV△T
beta is coefficient of volumetric expansion
Types of systems
Isolated systems
not capable of exchanging energy or matter with their surroundings
Closed systems
capable of exchanging energy, but not matter, with the surroundings
Open systems
can exchange both matter and energy with the environment
State functions
thermodynamic properties that are independent of the path taken to get to a particular equilibrium state
Pressure, density, temperature(not heat), volume, enthalpy, internal energy, gibbs free energy, entropy
Process functions on the other hand describe the path taken to get from one state to another
First law of thermodynamics
△U = Q - W
change in system’s internal energy = energy transferred as heat - work done by the system
change in internal energy = temperature
+q = heat into system
+w = work done by the system (expansion)
Three methods of heat transfer
Conduction is direct transfer of heat through molecular collisions
Convection is transfer of heat by the physical motion of a fluid over a material
Radiation is the transfer of energy by electromagnetic waves
Specific heat equation
q=mc△T
Cal to cal to J to BTU equation
1 Cal = 10^3 cal = 4200 J = 4 BTU
Heat of transformation equation
q=mL
L is latent heat
Types of thermodynamic processes
Isothermal - constant temperature
no change in internal energy
Adiabatic - no heat exchange
Isobaric - constant pressure
Isovolumetric (isochoric) - no volume change
Second law of thermodynamics
objects in thermal contact but not thermal equilibrium will transfer heat from higher temperature to lower temperature
-Isolated systems go towards higher entropy
Entropy equation
entropy is the heat gained or lost in a reversible process divided by the temperature in kelvin
△S = Qrev/T
when energy is distributed into a system at a steady temperature, entropy increases
Restating the second law in an equation
△Suniverse = △Ssystem + △Ssurroundings > 0
simple density equation, density of water (which unit is 1000?)
p = m/V
density =mass/volume
density of water = 1g/cm^3 or 1000kg/l^3
Finding the density of a fluid from weight and volume, or vice versa
Fg(weight) = pVg
Weight = density * volume * gravity
(F=ma with m = density*volume)
Specific gravity
Specific gravity is a unitless ratio of density/density of water
Ex: 877kg/m^3 =.877 specific gravity
Simple pressure equation
P = F/A
Absolute pressure and equation
Absolute pressure (hydrostatic) is the total pressure exerted on an object that is submerged in fluid (both liquid and gas)
P = p0 + pgh
P is absolute pressure, P0 is incident or ambient pressure, p is density of fluid, g is acceleration due to gravity, and h is depth
P0 is often atmospheric pressure but not always
Fluid pressure equation
Pf = pgh
density of fluid * gravity * depth
Conversion between Pa, mmHG, torr, and atm
10^5 Pa = 760mmHG =760 torr = 1 atm
Gauge pressure and equation
Gauge pressure in the difference in atmospheric pressure and absolute pressure
Pgauge = Pressure - Patm = (pgh) - Patm
pgh = densitygravitydepth
(Absolute pressure is gauge pressure measured in a vacuum)
Hydraulic systems principles equations
a change in pressure will be transmitted undiminished to every portion of the fluid an to the walls of the containing vessel
Hydraulic systems
P = F1/A1 = F2/A2
force and area are a fixed ratio for both sides of a hydraulic system (the force is proportional to the area)
V = A1d1 = A2d2
(Area)(distance) on both sides is equal (the distance is inversely proportional to the area)
Archimedes principle equation (Force of bouyancy)
Fbouyancy = pfluidVsubmergedg
Bouyancy force = weight of displaced fluid
Surface tension
results from cohesion between molecules due to IMFs
adhesion is the attractive force that a molecule of the liquid feels toward the molecules of some other substance
A meniscus occurs due to adhesion with the side of the container, a convex meniscus occurs when the adhesive forces are greater than cohesive forces
viscosity
viscosity (η) is the resistance of a fluid to flow
increased viscosity increases its viscous drag
-analogous to air resistance
those with lower viscosities behave more like ideals fluids, which are inviscid
-we assume this for the MCAT
Poiseulle’s Law (Laminar flow)
Laminar flow, can be modeled through Poiseuille’s Law
Q = ΔPπr^4 / 8ηl
pay attention to:
radius to the fourth power and pressure change on the numerator
viscosity and length are the denominator
Turbulent flow
Turbulent flow is rough, causes formation of eddies
eddies are swirls of fluid of varying sizes
laminar flow occurs at the boundaries in a boundary layer
can arise when the speed of the fluid exceeds a certain critical speed
critical speed equation
vc = Nrη / pD
vc is the critical speed Nr is a constant called the Reynolds number η is viscosity p is density of the fluid D is diameter of the tube
Most likely just need to understand the concept/relationships
flow rate and linear speed through a pipe equation
Q (flow rate) = v1 (linear speed) * A1 (cross sectional area)
Area = pi*r^2
Bernoulli’s equation
P + 1/2pv^2 + pgh = CONSTANT
Pressure energy + Kinetic energy + pressure is constant
P is absolute pressure, p is density, v is linear speed, g is gravity, h is average height of flow
velocity and pressure are inversely related
electrostatic force between two charges
Fe = kq1q2/r^2
similar to gravitational force, with k instead of G and q instead of m
quantities the magnitude
repulsive forces lead to positive electrostatic force
Energy of an electric field equation
E = Fe / q = kQ / r^2
equal to the electrostatic force divided by charge placed in the electric field
Q is stationary source charge that creates the electric field
Electric potential energy equation
U = kQq/r
similar to gravitational energy in the same way as the electrostatic force is similar to the gravitational force
energy ends with /r, force ends with /r^2
repulsive forces lead to positive energy
Electric potential equation
a charges potential energy divided by the magnitude of its charge
V = U/q = kQ/r
measured in volts
Potential difference
Difference in electric potential
potential difference between two charges gives voltage
ΔV = Vb - Va = Wab/q
Wab is the work needed to move a test charge q through an electric field from point a to b
Equipotential line
An equipotential line is a line on which the potential at every point is the same
the potential difference between any two points on an equipotential line is zero
Electric dipole and dipole moment
results from two equal and opposite charges being separated a small distance d from each other
dipole moment is a vector that is a product of charge and separation distance
p = qd
magnetic field equation for a straight wire, direction of field vectors
All moving charges create a magnetic field, field lines point from north to south
B = μ0I / 2πr
B is the magnetic field, μ0 is the permeability of free space, I is the current, r is the distance from the wire
The direction of the field vectors can be determined using the right hand rule (I)
point your thumb in the direction of the current, your fingers will wrap in a way that mimics the circular field lines
magnetic field equation for the center of the circular loop
B = μ0I / 2r for the magnitude of the magnetic field at the center of the circular loop
Units for magnetic field
Tesla and gauss are the units for magnetic field strength, one tesla = 10^4 gauss
Diamagnetic vs paramagnetic vs ferromagnetic
Diamagnetic materials have no net magnetic field and are slightly repelled by a magnet
wood, plastic, water, glass, skin
Paramagnetic materials have unpaired electrons and will become slightly magnetized
aluminum, copper, gold
Ferromagnetic materials have unpaired electrons and will become strongly magnetized
iron, nickel, cobalt
Magnetic force and equation with respect to a charge
FB = qvBsinθ
q is the charge, v is the magnitude of its velocity, B is the magnitude of the magnetic field, and θ is the smallest angle between the velocity vector v and the magnetic field vector B
Magnetic force and equation with respect to a current carrying wire
For a current carrying wire: FB = ILBsinθ
where I is the current, L is the length of the wire in the field, B is the magnitude of the magnetic field, and θ is the angle between L and B
determining the direction of the magnetic force on a moving charge
the direction of the magnetic force on a moving charge can be determined using a right hand rule (II)
thumb in the direction of the velocity vector, fingers in the direction of the magnetic field lines.
Your palm will point in the direction of the force vector for a positive charge, whereas the back of your hand will point in the direction of the force vector for a negative charge
Metallic vs electrolytic conductivity
Metallic conductivity
metallic bond can be visualized as a sea of electrons flowing over and past a rigid lattice of metal cations
Electrolytic conductivity
not substantially different from metallic conductivity, but depends on the strength of the solution
Current equation and patterns of flow
Current is the amount of charge passing through the conductor per unit time
I = Q/Δt
unit of Ampere (1A = C/s)
two patterns of flow, direct current and alternating current
potential difference, voltage, and electromotive force
Potential difference (voltage) can be produced by an electric generator, galvanic cell, etc
When no charge is moving between the two terminals of a cell that are at different potential values, the voltage is called the electromotive force (emf)
Resistance of a resistor calculation
On a resistor, calculated using R = pL/A
p is the resistivity
Relationship between voltage, current, and resistance formula
V = IR
voltage is measured in Ohms
Internal resistance affect on current equation
Internal resistance lowers the amount of voltage supplied to a circuit through the equation:
V = Ecell - I(r)
Ecell is emf of the cell, I is the current, r is the internal resistance
Simple power equation
P = W/t = ΔE/t
Power equations with respect to current, voltage, and resistance
Power is the current times voltage drop
P = IV
and the current^2 times resistance if combined with Ohm’s Law
P = I^2R
and the voltage squared divided by resistance if combined with Ohm’s law
P = V^2/R
Resistors in series or parallel equation
Resistance is additive in series
Rtotal = R1 + R2 …
In parallel it decreases
1/Rtotal = 1/R1 + 1/R2 …
Simple capacitance equation
Capacitance is defined as the charge over voltage
C = Q/V
unit of farad
Capacitance of parallel plate equation
Electric field equation
In a parallel plate, C = ε0(A/d)
A is the area of overlap of the two plates and d is the separation, ε0 is permittivity constant
Separation of charges sets up a uniform electric field, calculated as E = V/d
(this can be used for the cell membrane)
Potential energy stored in a capacitor equation
U = 1/2CV^2
affect of dielectric materials on capacitance equation
insulation, when introduced in between the plates of a capacitor it increases the capacitance by a factor called the dielectric constant
C’ = kC
with k being the dielectric constant and C being the old capacitance
change in voltage when a dielectric is placed in an isolated capacitor vs circuit capacitor
when a dielectric is placed in an isolated, charged capacitor, the voltage decreases
- this increases capacitance as a result
- due to the dielectric material shielding the opposite charges from each other
when a dielectric is placed in a circuit capacitor (still connected to a voltage source) the charge increases, but the voltage remains constant
-This increases the capacitance
Capacitors in Series or Parallel equation
Capacitance decreases in series
1/Ctotal = 1/C1 + 1/C2 …
Capacitance is additive in parallel
Ctotal = C1 + C2 …
opposite of resistance
Ammeters, Voltmeters, and Ohmmeters
Ammeters
used to measure the current at some point within a circuit, requires the circuit to be on
ideal have zero resistance
Voltmeters
like an ammeter, but used to measure the voltage drop across two points
Ohmmeters
does not require a circuit to be active, have their own battery of known voltage
Sinusoidal waves and types
Primary focus of MCAT, the individual particles oscillate back and forth with a displacement that follows a sinusoidal pattern
Transverse waves
Those in which the direction of particle oscillation is perpendicular to the propagation of the wave
EM waves (visible light, etc)
Longitudinal waves
Ones in which the particles of the wave oscillate parallel to the direction of propagation; in the direction of energy transfer
exhibit cycles of compression and rarefaction (decompression)
slinky flat on a table top and tapping it
propagation speed of waves
propagation speed (v) = frequency (f) * wavelength (λ)
must understand this relationship well
Period and frequency relationship of waves, angular frequency
Period (T) = 1 / frequency (f)
This equation can be reversed too, know that they are inversely related
Maximum phase difference
180 degrees
angular frequency
angular frequency (ω) = 2πf = 2π/T
Constructive and destructive interference
constructive interference
when the waves are perfectly in phase
destructive interference
when the waves are perfectly out of phase
noise-cancelling headphones
partially constructive or partially destructive interference
when the waves are not perfectly in or out of phase
resonance, timbre, forced oscillation, and natural frequency
objects have natural frequencies at which they vibrate
the quality of the sound, called timbre, is determined by the natural frequency or frequencies of the object
sounds that we don’t consider musical are called “noise”
forced oscillation
- if a periodically varying force is applied to a system, the system will be driven at a frequency equal to the frequency of the force
- example: if the force frequency is identical to the swing of a swingset, the swing becomes larger
if the frequency of the periodic force is equal to the natural frequency of the system, the system is said to be resonating
attenuation
a decrease in amplitude of a wave caused by an applied or nonconservative force
sound is subject to the same nonconservative forces as any traveling object
What is sound?
a longitudinal wave transmitted by the oscillation of particles in a deformable medium
produced by the mechanical disturbance of particles in a material
speed of sound related to bulk modulus and density and equation
speed of sound is equal to the square root of the bulk modulus divided by the density of the medium
V = sqrt(B/p)
bulk modulus increases from gas to solid more than density increases
pitch; infrasonic and ultrasonic
our perception of the frequency of sound
below 20Hz is infrasonic, above 20,000Hz is ultrasonic
Doppler effect and formula for different directions
frequency we perceive depends on the speed and direction of the object producing the sound
f’ = f(v-vo)/(v-vs)
- vd is speed of detector, vs is speed of source
- this setup is if the source is chasing the observer
f’ = f(v+vo)/(v+vs)
-this setup is if the observer is chasing the source
f’ = f(v+vo)/(v-vs)
- this setup gives the maximum observed freq, with both moving towards each other
- because the source is on the bottom, it moving away from the observer causes the observed frequency to increase. because the observer is on the top, it moving towards the observer causes the observed frequency to increase
used in echolocation
Shock wave
special case of the doppler effect
an object is producing sound while traveling at or above the speed of sound
allows wave to stack, creating very high amplitude
- this causes a highly condensed wave called a shock wave
- high pressure followed by low pressure creates a sonic boom
Intensity equation
Intensity = Power / Area I = P/A
Decibel equation
ß = 10logI/I0
ß = sound level, I = intensity of sound wave, I0 = threshold of hearing
a sound level of 0dB is 10^-12 W/m^2
a sound level of 100dB is 10^-2 W/m^2
equation for combining two sound levels
Sound level is additive
new sound level can be taken by adding past sound level and new one calculated using equation above
Beat frequency and equation
periodic increase in volume due to a difference in pitch
fbeat = f1 - f2
type of boundary and type of node in standing waves
Standing waves contain nodes and antinodes
closed boundaries do not allow oscillation, correspond to nodes
nodes have no fluctuation in displacement
open boundaries allow maximal oscillation and correspond to antinodes
antinodes have maximum fluctuation in displacement
wavelength of a standing wave and the length of string that supports it equation
wavelength of a standing wave and the length of string the supports it is:
λ= 2L / n
λ is wavelength, L is length, n is harmonic number (integer)
possible frequencies of a string equation
f = nv / 2L
v is wave speed
harmonic number
number of half-wavelengths supported by the string
doubling doubles the frequency and halves the wavelength
all the possible frequencies that the string can support form its harmonic series
open pipe and first harmonic
has antinodes at both ends
if only one node in between, length equals half of the wavelength of the standing wave (first harmonic)
closed pipe and first harmonic
has nodes at closed end, antinode at open end
-first harmonic corresponds to only those two, length equals one quarter wavelength of the standing wave per each harmonic
usage of ultrasound
Ultrasound can be used in diagnostics (imaging) or therapy (increases blood flow)
Order of electromagnetic spectrum
From longest to shortest:
Radiowaves, microwaves, infrared, visible light, ultraviolet, x-ray, gamma rays
Rabbits mate in very unusual expensive gardens
Order of visible lights with wavelengths
from longest to shortest
700nm to 400nm
Roy G Biv
speed of light equation
speed of light = frequency times wavelength
c = fλ
Reflection and equation
the rebounding of incident light waves at the boundary of a medium
Angle of incidence equals angle of reflection from the normal
θ1 = θ2
-this is the angle from normal, not the ground
Real reflection
an image is real if the light converges at the position of the image
always inverted
Virtual reflection
an image is virtual if the light only appears to be coming from the position of the image but does not actually converge there
always upright
Plane mirrors
causes neither convergence or divergence of reflected light ways
reflection is always virtual
-appearance of light from behind the surface
can be conceptualized as spherical mirrors with an infinite radius of curvature
Spherical mirrors
have an associated radius of curvature
center of curvature is the center of the theoretical circle if the mirror were a complete sphere
Concave mirrors are called converging mirrors and convex mirrors are called diverging mirrors
focal length master equation and interpretation
1/f = 1/o + 1/i = 2/r
focal length = radius of curvature / 2
1/focal length = 1/object distance + 1/image distance
if image distance is positive, it indicates a real image (in front of the mirror)
if the image distance is negative, it indicates a virtual image (behind the mirror)
magnification equation and interpretation
m = -i / o
magnification is the negative ratio of the image distance to the object distance
negative magnification signifies an inverted, real image
positive magnification signifies an upright, virtual image
if ImI < 0, image is reduced, opposite is enlarged
object distance is always positive for MCAT
image distance is positive if real, negative if virtual
adding together the magnification of multiple lens
m1 x m2 x m3 . . .
magnification is multiplicative
Image from converging mirror/lens with varying distances from the mirror/lens
Object = one focal length away: no image is formed
Object < one focal length away: image is upright, virtual, magnified
-the light has not converged yet
Object > one focal length away: image is inverted, real, and magnified
Image from diverging mirror/lens with varying distances from the mirror/lens
image is always upright, virtual, reduced
- light cannot converge in a diverging system
- appears closer to mirror than it is
speed of light in a new material equation
speed of light always less than c unless in a vacuum
n = c/v
n is a dimensionless quantity called the index of refraction, v is speed of light in the medium
index of refractions of air, water, glass, diamond
air = 1 water = 1.33 glass = 1.5 diamond = 2.4
Snell’s law (angle of refraction)
n1sinθ1 = n2sinθ2
theta is still measured with respect to the normal
light always bends towards the normal in a medium with a higher index of refraction
Total internal reflection and equation
θc = sin^-1(n2/n1)
If the angle is above this angle, the refracted light ray passes along the interface between the two media
Lensmaker’s equation for when the thickness of a lens cannot be neglected (focal length, index of refraction, and radius of curvatures)
1/f = (n-1)(1/r1 - 1/r2)
f is focal length, n is index of refraction for the lens, r1 is the radius of curvature for first lens surface, r2 is radius of curvature for the second lens surface
focal distance equation of a lens
1/f = 1/o + 1/i = 2/r still applies for lens
a positive i still indicates that the image is real, which now means it was on the opposite side of of the light source
convex lens is converging, while concave lens is diverging
-opposite of mirror
Power of a lens equation, sign for converging vs diverging lens
measured in diopters, inverse of focal length
P = 1/f
P has the same sign as f, and is therefore positive for a converging lens (convex) and negative for a diverging lens (concave)
how to add together the power of multiple lens
how to add together the focal length of multiple lens
P1 + P2 + P3 . . .
Power is additive, which means focal length adds like:
1/f1 + 1/f2 + 1/f3 …
Spherical aberration
a result of imperfect lens in which there is a blurring of the periphery of an image as a result of inadequate reflection of parallel beams
very slightly different image distances at the edge of the imag
Dispersion
when various wavelengths of light separate from each other
violet light is the smallest wavelength and bends the most
if n = c/v, wavelength can change with respect to n if the speed of light is the same
Chromatic aberration
depending on the thickness and curvature of of the lens, there may be a significant splitting of white light
Diffraction; maxima and minima
the spreading out of light as it passes through a narrow aperture or around an obstacle
Creates maximum (central bright fringe) and minima (location of dark fringes) maxima are places of constructive interference while minima are positions of destructive interference
Diffraction gratings
Diffraction gratings consist of multiple slits arranged in patterns
Can create colorful patterns similar to a prism as the different wavelengths interfere in characteristic patterns
grooves on a DVD, thin films like soap bubbles or oil puddles
X-ray diffraction
uses the bending of light rays to create a model of molecules
dark and light fringes do not take on a linear appearance, but rather a complex two dimensional image
Plane polarized light
the electric fields of all the waves are orientated in the same directions
used to determine chirality
Circular polarization
rarely seen phenomenon, interaction of light with certain pigments or highly specialized filters
uniform amplitude but continuously changing direction
Photoelectric effect
When light is incident on a metal in a vacuum, the metal atoms emit electrons. Electrons liberated will produce a net charge flow per unit time, or current
occurs in chlorophyll
Supports the particle theory of light
Threshold frequency of light and equation
the minimum frequency of light that causes ejection of electrons
Photoelectric effect is an all or nothing response
E = hf
the energy of each photon is proportional to the frequency of the light multiplied by planck’s constant h
lower frequency = higher wavelength = lower energy
kinetic energy of ejected electrons equation
Kmax = hf - BE
Maximum kinetic energy of the ejected electron = photon energy - binding energy/ work
h is planck’s constant
Work = BE = hf0
where f0 is threshold frequency
minimum energy required to eject an electron, related to the threshold frequency of the metal
kinetic energy can be anywhere from zero to maximum
Nuclear binding energy, mass defect and equation, and strong nuclear force
The actual mass of every nucleus is slightly smaller than the masses of the protons and neutrons
E = mc^2
calculates the mass defect, c is the speed of light
the mass defect is a result of matter that has been converted to energy
A strong nuclear force keeps protons and neutrons together
-very short range but very strong
Binding energy is the energy needed to decompose the nucleus into separate protons and neutrons
- exactly the same magnitude as the mass defect
- intermediate-sized nuclei are the most stable
Atomic number
Z- number of protons
Mass number
A- number of protons and neutrons
Fusion
small nuclei combine to form a larger nucleus
mass defect is emitted
Fission
large nuclei split into smaller nuclei
spontaneous fission rarely occurs, but can be induced through the absorption of a low-energy neutron
Radioactive decay
Naturally occurring and spontaneous
Atomic number and mass number must be the same on both sides of the equation
Alpha radioactive decay
an alpha-particle is a He nucleus
two protons, two neutrons
the atomic number of the daughter nucleus will be two less than that of the parent nucleus, and the mass number will be four less
Beta radioactive decay
a beta particle is an electron
beta- decay is the loss of an electron
the atomic number of the daughter nucleus will be one higher, but the mass number will not change
beta+ decay is the loss of a positron
the atomic number of the daughter nucleus will be one lower
in some cases of induced decay
Gamma radioactive decay
a gamma ray is a high energy photon, carries no charge
simply lower the energy of the parent nucleus without changing the mass number or the atomic number
Electron capture radioactive decay
rare process where an inner electron combines with a proton to form a neutrino
decreases the atomic number by one
-the reverse of beta- decay, the same as beta+ decay
Half-life
time it takes for half the sample to decay
What to do if you are give an e value with a decay question?
multiply original mole amount times the e value to get the moles of product
Converting between scientific notation (Ex: 10^-3 =?)
10^3 = + ,000
10^-3 = - ,000
logarithmic base 10 estimation (ex: log1000)
log(10n) = n
the times 10 needs to be multiplied by itself to equal the number
log1000 = 3
estimating pH
If [H+] = m x 10^-n , pH ≈ n-1.10-m or n-.m
FINER method
The FINER method assesses the value of a research question on the basis of whether or not it is feasible, interesting, novel, ethical, and relevant
positive vs negative controls
positive controls ensure that a change in the dependent variable occurs when expected
negative controls ensure that no change in the dependent variable occurs when none is expected
Accuracy vs precision
Accuracy is the quality of approximating the true value
Precision is the quality of being consistent with approximations
Hill’s criteria
Causality in observational studies is supported by Hill’s criteria, which include temporality, strength, dose-response relationships, consistency, plausibility, consideration of alternative explanations, experiments, specificity, and coherence
Medical ethics
Medical ethics includes Beneficence Nonmaleficence autonomy justice
Internal vs external validity
Internal validity refers to the identification of causality in a study between the independent and dependent variables
External validity refers to the ability of a study to be generalizable
Statistical vs clinical significance
Statistical significance refers to the low likelihood of the experimental findings being due to change
Clinical significance refers to the usefulness or importance of experimental findings to patient care or patient outcomes
Force of charged particle in a magnetic field formula
F = qvBsin(theta)
theta is the angle between velocity and magnetic field
Magnetic force for a wire exposed to a magnetic field formula
F = ILBsin(theta)
theta is the angle between field and wire
B is magnetic field, I is current, L is length of wire
How does a magnetic field do work on a charged particle?
It doesn’t, it just redirects the energy. (No change in velocity, only direction)
Right hand rule for where a particle would go if it experiences a magnetic field
The direction of the magnetic force F is perpendicular to the plane formed by v and B
With a flat hand, Magnetic field is index finger, velocity is thumb, and force is the direction of the palm
Electric Field Equation
E = V/d
(Volts/meter) = Volts/meter
