Chapter 13 - Electromagnetic Wave Model

Who discovered the relationship between current carrying conductors and induced magnetic fields?

oersted and Ampere

What is the name of the relationship Oersted and Ampere discovered?

Motor effect

How does the relationship Oersted and Ampere discovered work?

Constant electric current in a conductor induces a uniform constant magnetic field that circles the conductor

in which direction is the electric current in respect to the magnetic field?

perpendicular

who discovered the converse relationship to the motor effect

Henry and Faraday

what is the converse relationship to the motor effect called?

generator effect

how does the generator effect work?

when a conductor moves through a perpendicular magnetic field

what is an essential ingredients in the generator and motor effect?

a conductor

why could an insulator not be initially used for the generator and motor effect?

insulators resist the flow of electric current

What did Maxwell discover?

electricity could be induced in an insulator in the presence of an external magnetic field

What did the induced magnetic field cause?

a shift of charges

what happens to the shift of charges in the insulator?

the attractive forces soon pulled them back into place

so what was the core discovery of maxwell's experiments (conductor

insulator

where did maxwell discover electric/magnetic fields could exist?

in space

how did maxwell change amperes principle of magnetic induction (motor effect)?

a changing electric field in SPACE will generate a changing magnetic field in SPACE that is perpendicular to the electric field

how did maxwell change amperes principle of magnetic induction (generator effect)?

a changing magnetic field in SPACE will generate a changing electric field in SPACE that is perpendicular to the magnetic field

how does maxwell's theory for generator and motor effect work together?

A changing electric field induced a changing magnetic field which induces a new changing electric field which induces a new changing magnetic field which goes on....

at did maxwell's theory prove the generation of?

electromagnetic waves

what would emr be in these new generators/motors?

a self generating sieries of field radiating outward into space

what is emr also known as?

light

in which direction would an electromagnetic wave move in?

propagate in a direction perpendicular to both the electric and magnetic field

where coule emr travel?

through a vaccum?

why can emr travel through a vacuum?

does not require a medium and it could be polarized since it was transverse

REVIEW: what is a longitudinal wave?

compression and rarefaction; slinky

REVIEW: what is a transverse wave?

spotify

what is the primary cause of all electromagnetic waves

an accelerating electric charge

what happens when the electric charge is accelerated in periodic motion?

frequency of oscillation of the charge will correspond exactly to the frequency of the electromagnetic wave that is produced

what speed to all electromagnetic waves travel at?

speed of light (3E8 m/s)

how will electric and magnetic fields behave when the electromagnetic wave is involved?

they will be perpendicular to each other and the propagation of the wave

what phenomena do electromagnetic waves show?

all the phenomena involved with transverse waves

what are the phenomena associated with transverse waves?

interference

what is interference?

2 waves slamming into each other

what is diffraction

Apparent bending and spreading of waves around corners

what is refraction?

Bending of the waves as they pass from one medium to another with different speeds

what is polarization?

Orientation of the wave oscillations

what should emr produce when in contact with a surface?

pressure

who conducted experiments to confirm maxwells ideas?

hertz

what did hertz use in his experiment

induction coil to produce a spark across a gap

what are the 2 basic ways we see light?

light is emitted from a source of some kind

we also see light that is reflected from an object of some kind

how many basic properties of light are there?

3

how does light travel?

in straight lines

what is lights motion in straight lines refered to as?

rectilinear propagation

what is rectilinear propagation caused by?

changing electromagnetic radiation

what is evidence of rectilinear propagation?

shadows and how light does not bend around corners

what laws does light obey?

the laws of geometry

what speed does light have in a given medium?

In a vacuum/air light speed = 3E8 m/s

In water light speed = 2.68E8 m/s

who began the first successful demonstration of the speed of light?

olaf romer

what happens to the distance if we are speaking of a signal going to a place and back?

it is doubled

what is a light year?

Measure of distance for celestial objects; distance light travels in one year

what does the angle of incidence equal in the law of reflection?

angle of reflection

what is the angle of reflection/incidence always measured from?

the normal

where do incidence rays

normal

what happens when a bundle of parallel rays strike a smooth surface?

they obey the law of reflection and emerge as reflected parallel rays

what happens when parallel rays strike a rough surfface?

they will not be reflected as parallel rays

where do images of objects exist in a plane mirror?

within the mirror

what is a virtual image?

images that exist inside the mirror

What is a real image?

images that can be projected onto a screen outside the mirror

what is the normal for a spherical mirror?

the radius of the sphere

what are the two types of spherical mirror?

converging and diverging

what is a converging mirror?

light reflects toward the focal point

what is a diverging mirror?

light reflect away form the imaginary focal point

what are the 3 rays we use for ray diagrams?

parallel to focal

focal to parallel

center to center

what is the focal point of a mirror?

half of the radius of curvature for an image

when is the focal point positive? negative? (mirror)

for converging/concave mirrors

for diverging/convex mirrors

tell me what each variable stands for in this order? R

f

what sign does do always have?

always +

when is di positive? Negative?

positve for a real image

negative for a virtual image

what sign does ho always have?

positive

when is hi positive? negative?

• for erect orientation

• for inverted orientation

what happens at any interface between 2 mediums?

some light will be reflected and some light will be refracted

what do we do when we are solving refracted rays questions?

only pay attention to the refracted rays

what is the speed light travels in a vaccum?

3E8 m/s

What is the index of refraction?

the ratio of the speed of light in a vaccum with the speed of light in a medium

what is the formula for the index of refraction?

n = c/v

what is the index of refraction for a vaccum? air? water?

1.0000

what is refraction (snells)?

Change in speed (1)

what is the law we use to solve refraction problems?

snells law

what happens when we are refracting with parallel sides?

the original angle of incidence = the final angle of refraction

what happens when we are refracting with triangular prisms?

the sides are not parallel

when does total internal reflection occuer?

from high n to low n

what are the angles in total internal reflection?

the angle of refraction is greater than the angle of incidence

what does the refracted angle end up being in total internal reflection?

90 degrees

what is the definition of total internal reflection?

At angles beyond the critical angle

What is the critical angle?

the angle of incidence

what happens when angles are beyond the crtical angle?

then the media acts as a mirror surface

where is total internal reflection used?

fibre optics

when does total internal reflection occur (speeds)?

low to high speed media (high n to low n)

what do lenses involve?

refraction

what are convex lenses?

convergent

what are concave lenses?

divergent

why does something blur through a lens?

The light rays are parallel as the object is at the focal point

what are the equations for lenses?

the same as the ones for spherical mirrors

where do real images form for lenses? virtual?

behind a lens