• List four members of the electromagnetic spectrum. Two examples are light and radio waves.

S-58How are electromagnetic waves different from mechanical waves?

SPS9 Students will investigate the properties of wavesa. Recognize that all waves transfer energyb. Relate frequency and wavelength to the energy of different types of electromagnetic

waves and mechanical waves.c. Compare and contrast the characteristics of electromagnetic and mechanical (sound)

waves.d. Investigate the phenomena of reflection, refraction, interference, and diffraction.

Chapter 18

The Electromagnetic Spectrum and Light

How are electromagnetic waves different from mechanical waves?What is the maximum speed of light?How do electromagnetic waves differ from one another?What is the dual nature of electromagnetic radiation?What happens as light travels farther from its source?

18.1 Electromagnetic Waves

• Electromagnetic Waves – transverse waves that have a changing magnetic field and a changing electric field– Produced when an electric charge vibrates– Do not need a medium – Transfer of energy by electromagnetic

waves is called electromagnetic radiation (EMR)

18.1 Electromagnetic WavesHow are electromagnetic waves different from mechanical waves?

• All electromagnetic waves travel at 300,000,000 m/s in a vacuum– Maximum speed in the universe– Goes slower in other media– 186,000 mi/s

18.1 Electromagnetic WavesWhat is the maximum speed of light?

Porsche 918 Spyder

Plug in Hybrid

98 mpg

198 mi/hr (0.055 mi/s)

• Electromagnetic waves still follow the wave equation

– The speed is always 300,000,000 m/s – For vacuum – really close for air too, so

we use the same number– If frequency increases, then wavelength

decreases

18.1 Electromagnetic WavesHow do electromagnetic waves differ from one another?

v=f

• Electromagnetic waves sometimes behaves like a wave and sometimes like a stream of particles– travels through a vacuum – particle

because waves need a medium – Light refracts – wave because particles

don’t bend their path as they change mediums

– Einstein – photons – wave packets of energy

18.1 Electromagnetic WavesWhat is the dual nature of electromagnetic radiation?

• A. What is the speed of light in a vacuum?

• B. If a light beam has a wavelength of 6.33x1011 m, what is the frequency?

S-60How do electromagnetic waves differ from one another?

What waves are included in the electromagnetic spectrum?

How is each type of electromagnetic wave used?

18.2 The Electromagnetic Spectrum

• The electromagnetic spectrum includes many waves – the following are listed in order of increasing frequency, decreasing wavelength, and increasing energy.

• Radio• TV• Microwaves• Radar

18.2 The EM SpectrumWhat waves are included in the electromagnetic spectrum?

• Infrared• Visible Light• Ultraviolet• X-Ray

• Gamma

• Radio Waves– Radio signals– TV signals– Microwaves

• Cooking, for a short frequency range• Cell phone transmission

– Radar (RAdio Detecton And Ranging)• Bounce off the object for distance• Can tell speed using the Doppler Effect

18.2 The EM SpectrumHow is each type of electromagnetic wave used?

• Infrared Rays– Transfer heat – Sensed by heat sensors in your skin

• Visible Light– The range that human eyes can detect– ROY G BIV (red, orange, yellow, green,

blue, indigo, violet)

18.2 The EM SpectrumHow is each type of electromagnetic wave used?

• Ultraviolet– Sterilizing items – Required to form vitamin D– Tanning and skin cancer

• X-Ray– Medical and safety– Can also cause cancers

18.2 The EM SpectrumHow is each type of electromagnetic wave used?

• Gamma Rays– Cancer treatment – Industry to check pipes– We are constantly bombarded by

Gamma rays from the sun

18.2 The EM SpectrumHow is each type of electromagnetic wave used?

• List 6 members of the EM spectrum in order of increasing energy.

S-61What waves are included in the electromagnetic spectrum?

• List 6 members of the EM spectrum in order of increasing wavelength.

S-62What waves are included in the electromagnetic spectrum?

What three types of materials affect the behavior of light?How does light behave when it enters a new medium?

18.3 Behavior of Light

• How light behaves when it strikes an object depends on the material the object is made of

• Transparent – allows most of the light to pass through it

• Translucent – allows light to pass through, but scatters the light

• Opaque – either reflects or absorbs the light that strikes it

18.3 Behavior of LightWhat three types of materials affect the behavior of light?

• A number of things can happen to light when it strikes a surface

• Reflection – the light waves bounce of the surface– Regular reflection – rays bounce off in an

orderly patter • Creates an image

– Diffused reflection – no pattern• Only color

18.3 Behavior of LightHow does light behave when it enters a new medium?

• Refraction – bending of light when it strikes a surface– Cause objects to look broken– Or even a mirage (light bending due to

different temperature layers of air)

• Polarization – when light only vibrates in one plane– Reduces glare

18.3 Behavior of LightHow does light behave when it enters a new medium?

• Diffraction – bending of light around barriers– A hole will act like a new source of the

wave– Ripple away from edge

18.3 Behavior of LightHow does light behave when it enters a new medium?

What determines the color of an object?What are the primary colors of light?What are the primary colors of pigments?

18.4 Color

• Color depends on – What the object is made of (what colors

it will absorb or reflect)– The color of light that strikes the object

18.4 ColorWhat determines the color of an object?

• Primary colors – three specific colors that combine to create all possible colors– Red, Blue, Green (RBG)– These colors combine to form the

secondary colors• Yellow, Cyan, Magenta

– The primary colors all combine to form White

18.4 ColorWhat are the primary colors of light?

• Pigment – a material that absorbs light– Paint– Primary pigments are

Cyan, Magenta, & Yellow

– Ink cartridge colors– They mix to form Black

18.4 ColorWhat are the primary colors of pigments?