Light

I. Electromagnetic Radiation

EM RadiationEM SpectrumTypes of EM Radiation

A. EM Radiation

Electromagnetic Radiationtransverse waves produced by the motion of electrically

charged particlesdoes not require a mediumspeed in a vacuum = 300,000 km/selectric and magnetic

components are perpendicular

A. EM Radiation

Photonstiny, particle-like

bundles of radiationabsorbed and released

by electronsenergy increases with wave

frequency

B. EM Spectrum

long

low f

low energy

short

high f

high energy

C. Types of EM Radiation

Radiowaveslowest energy EM radiation

C. Types of EM Radiation

RadiowavesFM - frequency modulation AM - amplitude modulation

Microwavespenetrate food and vibrate

water & fat molecules to produce thermal energy

C. Types of EM Radiation

Infrared Radiation (IR)slightly lower energy than

visible lightcan raise the thermal energy

of objectsthermogram - image made by

detecting IR radiation

C. Types of EM Radiation

Visible Lightsmall part of

the spectrum we can see

ROY G. BIV - colors in order of increasing energy

R O Y G. B I V

red orange yellow green blue indigo violet

C. Types of EM Radiation

Ultraviolet Radiation (UV)slightly higher energy than visible lightTypes:

• UVA - tanning, wrinkles• UVB - sunburn, cancer• UVC - most harmful,

sterilization

C. Types of EM Radiation

Ultraviolet Radiation (UV)Ozone layer depletion = UV exposure!

C. Types of EM Radiation

X rayshigher energy than UVcan penetrate soft tissue,

but not bonesUsed to be used to size

shoes before harmful affects were known.

C. Types of EM Radiation

Gamma rayshighest energy

EM radiationemitted by

radioactive atomsused to kill

cancerous cells Radiation treatment using radioactive cobalt-60.

CHECK UNDERSTANDING

1. A light wave is an electromagnetic wave that has both an electric and magnetic component associated with it. Electromagnetic waves are often distinguished from mechanical waves. The distinction is based on the fact that electromagnetic waves ______.

a. can travel through materials and mechanical waves cannot b. come in a range of frequencies and mechanical waves exist with only certain

frequencies c. can travel through a region void of matter and mechanical waves cannot d. electromagnetic waves cannot transport energy and mechanical waves can

transport energy e. electromagnetic waves have an infinite speed and mechanical waves have a finite

speed

Check Understanding

a. Which region of the electromagnetic spectrum has the highest frequency?

b. Which region of the electromagnetic spectrum has the longest wavelength?

c. Which region of the electromagnetic spectrum will travel with the fastest speed?

GAMMA RAY

RADIO WAVE

All waves have the same speed which depends on the medium

Check Understanding

a. Which color of the visible light spectrum has the greatest

frequency?

b. Which color of the visible light spectrum has the greatest

wavelength?

VIOLET

RED

Light

II. Light and Color Light and Matter Seeing Colors Mixing Colors

A. Light and Matter

Opaqueabsorbs or reflects all light

Transparentallows light to pass through completely

Translucentallows some light to pass through

B. Seeing Colors

White lightcontains all visible colors - ROY G. BIV

In white light, an object…reflects the color you seeabsorbs all other colors

REFLECTSALL COLORS

ABSORBSALL COLORS

B. Seeing Colors

The retina contains…Rods - dim light, black & whiteCones - color

• red - absorb red & yellow• green - absorb yellow & green• blue - absorb blue & violet

Stimulates red & green cones

Stimulates all cones

Video: How Cones and Rods Work

B. Seeing Colors

Color Blindnessone or more sets of

cones does not function properly

Test for red-green color blindness.

C. Mixing Colors

Primary light colors

red, green, blue

additive colors

combine to form white light

View Java Applet on primary light colors.

EX: computer RGBs

C. Mixing Colors

Filtertransparent material

that absorbs all light colors except the filter color

View Java Applet on filters.

C. Mixing Colors

Pigmentcolored material that absorbs

and reflects different colors

Primary pigment colorscyan, magenta, yellowsubtractive colorscombine to form blackEX: color ink cartridges

C. Mixing Colors

Light Pigment

When mixing pigments, the color of the mixture is the color of light that both pigments reflect.

Bill Nye Explains Color