Calculate the speed of a water wave when waves 5.0 m apart

pass by at 40.0 waves per minute

Chapter 16

Light

Light•The range of frequencies of

electromagnetic waves that stimulate the retina

of the eye

Electromagnetic Wave•Transverse waves made up of pulses

moving through space that affect both electric

& magnetic fields

Spectrum•An ordered

arrangement of many frequencies or

wavelengths of waves

Electromagnetic Spectrum•An ordered

arrangement of all the electromagnetic waves

Ray•The straight line

path of a light wave

Incident Ray•A ray striking a

surface

Transmitted Ray

•A ray passing through a substance

Reflected Ray•A ray bouncing off

of another substance

Speed of Light•First Determined by Ole Roemer by observing the

moons of Jupiter from opposite ends of Earth’s

orbit.

Speed of Light•Correctly determined by

Michelson by reflecting light from a spinning

octagonal mirror.

Speed of Lightcvac = 299,792,458 m/s

For most calculations:

c = 3.00 x 108 m/s

Light Velocity Formula:

c = f

Calculate the frequency of electromagnetic

waves at:600.0 nm150 m45.0 cm

Calculate the frequency of IR

light at:900.0 nm

Luminous•Anything that emits light

•Sun, light bulb, etc

Illuminated•Anything that reflects light

•Moon, mirror, wall, etc

Luminous Flux (P)

•The rate at which light is emitted

Lumens (lm)•The unit of luminous flux

Light from a bulb or source is emitted spherically from the

source

We are usually interested in the illumination of a

certain area

Illuminance (E)•The illumination of

a surface

Lux (lx)•The unit for illumination

•lx = lm/m2

Luminous Intensity (I)

•The magnitude of the light source

Candela (cd)•Candle power of

the unit for luminous intensity

Luminous Intensity Formula

I

d2E =

Luminous Flux Formula

P

4d2E =

Determine the effect on illumination of a wall if a light source is moved

from 30.0 to 120 cm away from the wall.

Calculate the illumination on a

surface 2.0 m away from a bulb emitting

1600 cd.

Calculate the illumination on a

surface 3.0 m away from a bulb emitting

2700 cd.

Transparent•Substances that allows

light to be clearly transmitted through

them

Translucent•Substances that allows light to be transmitted,

though not clearly, through them

Opaque•Substances absorb or reflect all light striking

them

Color• A perception caused when cones in the eyes are excited

by certain frequencies or wavelengths of

electromagnetic waves

Luminous Colors

Primary Colors•Red

•Blue

•Green

Secondary Colors•Colors produced by mixing primary colors

Secondary Colors•Yellow = Red + Green

•Cyan = Blue + Green

•Magenta = Red + Blue

Complimentary Colors

•Two colors that when mixed produced white

light

Complimentary Colors

•Red + Cyan

•Blue + Yellow

•Green + Magenta

List the three primary colors &

list each’s complementary

color.

Illuminated Colors

Dyes•Molecules that

absorb certain wavelengths of light;

thus reflect others

Dyes•Dyes are made up of molecules which are too small to be seen with a microscope

Dyes•When dissolved, form colored solutions that allow light to pass through

Pigments•Materials that absorb certain wavelengths of light; thus reflect others

Pigments•Pigments are made up of particles large enough to be seen with a microscope

Pigments•When dissolved, form suspensions that reflect light and are opaque

Primary Pigments

•A pigment that absorbs a primary color

Primary Pigments

•Yellow

•Cyan

•Magenta

Secondary Pigments

•A pigment that absorbs two primary colors; thus reflect the third

Secondary Pigments

•They are the primary colors: red, blue, & green

Thin Film Interference•Constructive &

destructive effects of interference causing a

rainbow appearance on a thin film

Thin Film Interference

•Wavelengths are reinforced when the film

is ¼ , ¾ , 5/4 , etc

Electromagnetic waves are transverse with vibrations like

sin waves vibrating at 360o from the ray

Polarized Light•A light wave

vibrating in only one direction

Polarized Light•Can be produced by passing regular light through a polarized

lens

Polarizer•A screen with very

fine slits all being parallel to each other

Calculate the frequency & period

of light with a wavelength of 450

nm