Physics Final Vocab

Equilibrium

Equilibrium

center of wave motion

Amplitude

maximum displacement from equilibrium. A traveling wave goes from +amplitude to -amplitude

Crest

positive amplitude

Trough

negative amplitude

Wavelength

distance from creast to crest (or trough to trough)

Frequency

measured in Hertz

Medium

the substance/material that the wave energy travels through

Wave motion

the motion of the individual particles of the medium

Transverse wave

wave where the direction of motion of the individual particles of the medium are perpendicular to the direction that the wave travels in.

Longitudinal wave

wave where the direction of motion of the individual particles of the medium are parallel to the direction that the wave travels in

Wave pulse

a single, non periodic excitation of a medium

Law of Reflection

relates the angle of the incoming or incident wave to the angle of outgoing or reflected wave (angles are always measured perpendicular to the surface) FOR MIRRORS

Law of Refraction

• If the wave hits the interface between the medium at an angle, the refracted wave angle changes according to Snell’s Law (only occurs when speeds of incident ray are different)

• faster medium = bigger angle

Snell’s Law

angle is draw perpendicular to the surface

sin(angle 1)/sin(angle 2) = (v1)/(v2)

Index of Refraction

Speed of wave in vacumn is always 3×10^8 m

n = c(speed of light)/v(material) = c

BIGGER N MEANS SLOWER INDEX OF REFRACTION

Snell’s Law with Index of Refraction

Refraction Concepts

in a new medium, the wave speed changes but frwquency is unchanged

• wavelength changes to match the wave equation

index of refraction is always greater than 1

Critical Angle

the angle the incident wave makes

Critical Angle Math

sin(angle) = n2/n1

Total Internal Reflection

After the critical angle is reached, none of the energy is transmitted. Instead, all of the energy is reflected.

Rainbows

The index of refraction is dependent on the frequency or wavelength of the light traveling through it

The different colors of white light get bent differently so the colors get separated.

Light properties

light is an electromagnetic wave (it has particle like porperties)

the speed of light eq is c= 3 × 10^8 ms^-1

wave eq for light is c = f*wavelength

wave reflection

Wave energy tends to reflect whenever the wave hits a change in medium

◦ Sound hitting a wall

◦ Water hitting the edge of a bowl

◦ Light hitting a mirror

wave superposition

two waves add together during the collison

the energy of the two waves continues in their original direction after the collision

interference

when two or more waves collide

Constructive interference

when the collision results in a larger amplitude than individual waves

destructive interference

when the collision results in a smaller amplitude

Antinode

point of maximum cconstructive interference; greatest movement

Node

point of maximum destructive interference; no movement

Standing Waves

When a wave collides with its reflection and the conditions are perfect a standing wave is created.

• Speed is controlled by the medium (v)

• Length is controlled by the setup (L)

• Frequency is controlled by the setup (f)

Harmonic

longest is the first harmonic or fundemental frequency

wavelength formula - harmonic

wavelength = 2L/number harmonic

frequency formula - harmonics

fn = number harmonic * frequency

sound

The wave is longitudinal.

The air molecules move back and forth, being compressed and stretched (compression/rarefaction).

sound is a wave

we use a number around 340 m/s

open-open air tube

open ends must be antinodes - the air has the most freedom to move

L = n(wavelength/2)

wavelength = 2L/n

Frequency at n harmonic = number harmonic x initial frequency

closed-open air tube

closed ends must be nodes - the air cannot move

L = n x (wavelength/4)

wavelength = 4L/number harmonic (but n can only be odd)

Frequency at n harmonic = number harmonic x intial frequency

doppler effect

the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave.

closer = higher freq; farther = lower freq

Vision

• light is an electromagnetic wave

  • generally travels in packet called photons and these packets travel in a straight line

• photons hit retina

• rods and cones convert light energy to neural signals

• photons can either be absorbed or reflected

object distance d0

the distance of the object to the mirror or lens

image distance di

the distance of the image to the mirror or lens

upright images

vertially oriented the same way as the object

inverted images

vertically oriented upside-down compared to the object

virtual images

appears on the other side of the mirror or lens from the observers viewpoint

real image

appears on the same side of the mirror or lens

magnified image

appears larger than the object

reduced or demagnified

appears smaller than the object

coverging

an optical device that focuses light rays (e.g. concave mirror or convex lens)

diverging

an optical device that spreads light rays out. The focal point is on the “wrong” side (e.g. convex mirror or concave lens)

plane mirror image

virtual image

appears upright, same size as object

d0 = di

spherical concave mirrors

designed to focus incoming light from far away on a single point called focal point

f is used to represent distance from mirror to focal point

center of curvature

spherical mirrors have a center of curvature

c is used to represent distance from mirror to center of curvature

c is equal to center of circle and distance to mirror/lens is radius of the circle

FOCAL POINT IS HALF THE RADIUS

c= 2f or f = c/2

spherical convex mirror

has a focal point is the point where the light rays appear to originate from

negative distance from the mirror

ray diagram

only draw 2 rays

image places where the reflected rays intersect

extend lines to achieve nessecary intersections

convex mirror

center of curvature and focal point are on opposite sides of mirror

flat (plane) mirror

has a radius of curvature of infinity

Lens Ray Diagram Rules

First Ray: Parallel to the first focal point and through it

Second ray: through the second focal point then parallel

Third ray: through the center of the lens itself

concave lens

follows the same ray diagram rules

focal points are reversed

f (distance from mirror to focal point) is negative

atoms

made up of protons nuetrons and electrons

Atoms are made up of……

protons, neutrons, electrons

What charge are protons?

positive

What charge are neutrons?

no charge

What charge are electrons?

negative charge

What is matter made up of?

atoms

The number of what in the atom determines the element?

protons

What is an isotope?

same number of protons but different number of neutrons

Does an atom USUALLY have an equal number of electrons and protons?

yes

what is an ion?

has an unequal number of electrons and protons

what are the units of charge?

coulombs ©

The charge of an electron is

-1.6 × 10^-19c

The charge of a proton is

+1.6×10^-19

What does “charge is quantized” mean?

charge comes in discrete amounts

What is the smallest unit of charge in physics?

1/3e

What charge is an atom usually?

neutrally charged

Removing electrons gives what charge……

positive charge

Adding electrons gives what charge…..

negative charge

Do protons move?

no

What is a conductor?

a material where the elctrons can move freely about (metals, wires, water)

has a lot of ions

What is an insulator?

a material where the electrons are not free to move

rubber glass air

What is a semi-conductor?

a special type of material that acts as both a conductor and insulator depending on the situation

can act like a switch letting electrons pass (conductor)

can block electrons from passing (insulator)

key to the information revolution

forces in decreasing order of strength

strong nuclear force, electromagnetic force, weak nuclear force, gravatational force

what is coulombs law?

describes force between two charged object

“The force between two charged objects is proportional to the product of the charges and inversely proportional to the square of the distance between the objects.”

opposite sign charges….

attract each other

Similar sign charges…

repel each other

a pair of forces is describes as

“attractive” or “repulsive”

electric force

use newtons

inversly proportional the the square of distance

measured from centers

proportional to the product of the two charges

very strong

attractive or repulsive

gravitational force

use newtons

inversely proportional to square of distance

measured from centers

proportional to product of the two masses

very weak

attractive only

unit for charge

ways to charge

rubbing

contact (conduction)

induction

polarization

contact/conduction

When a conducting object is charged (either negatively or positively), that charge can be shared with other conducting objects by touching the objects together

induction

Charging by induction does not require touching, but does require a source (or sink) for electrons to travel from (or to)

rubbing

one object will become positive and one object will become negative

ONLY ELECTRONS MOVE NEVER PROTONS

polar

partial charges

polarization

charges shifted slightly to one side

overall nuetral

positive on one side and negative on the other

electric potential

two stored energy assosciates with two charges held in position'

same as voltage

formula is V = K * Q/r

equipotential lines

always drawn perpendicular to the electrical field

electrical field always goes in direction of decreasing voltage

uniform electrical field

formula: change in voltage = Ed

equipotential lines are parallel to plates

electric potential at multiple charges

the electric potential at a given points is the sum of the electric potential from each charge (keep sign from charge)

work on a charge

equipotnetial lines assist in calculating work on a charge and therefore kenetic energies

w= -q(change in V) = change in KE

if a charge moves from VOltage A to Voltagee B then the field does work on the charge

thin lens formula

1/f = 1/do + 1/di

convex mirror and cocave lens

negative focal point

magnification

M = hi/ho = -di/do

all real images are inverted

real distances are positive

virtual distances are negative

|M| > 1 magnified

|M| < 1 means reduced