1. Light
Investigate the properties and behaviors of mechanical and electromagnetic waves
Explore and explain the nature of sound and light energy

2. Electromagnetic Waves
Transverse waves of electric and magnetic fields
Electric field-electric force on charged particles
Magnetic field-magnetic force
Produced when electric charge vibrates or accelerates
Do not need a medium
Can travel through a vacuum or matter

3. Properties of Electromagnetic Waves
Speed of Light is 3.00 x 108 m/s
Have wavelength and frequency, n=lf
Sometimes act like waves
Destructive and constructive interference
Sometimes act like particles
Can hit metal and release an electron, photoelectric effect
Photons, packets of energy
Intensity decreases as distance increases

4. Electromagnetic Spectrum
Radio waves
Infrared rays
Visible light
Ultraviolet light
X-rays
Gamma rays

5. Radio Waves Frequencies of 300 GHz to 3 kHz
Wavelengths of 1mm to 100 km
Used in radios, television, radar, and microwaves
Radios require a tuner to select specific frequencies
In radar radio waves hit an object and bounce back to detector
In microwaves, waves cause water to vibrate and heat food
Also used in MRIs

6. Infrared Rays Wavelengths of 750 nm to 1 mm
Frequencies of 1 THz to 400 THz
Sense as heat
Thermograms show heat regions
Used in chemistry to determine molecules
Used to see underlying images in paintings

7. Visible Light Frequencies of 400 THz to 750 THz
Wavelengths of 400 nm to 750 nm
Each wavelength is a specific color
ROYGBIV

8. Ultraviolet Rays Higher frequencies than violet light
Wavelengths of 400 nm to 4 nm
Helps create vitamin D but can also cause skin cancer

9. X-rays Wavelengths of 12 nm to 0.005 nm
High energy, can go through media visible light cannot
Absorbed by bones and teeth to create images
Can also kill tissues
Used in airport security

10. Gamma Rays Wavelengths less than 0.005 nm Extremely high frequencies
Very high energy, very dangerous
Used to kill cancer cells by pinpointing specific spots
Can be used in brain scans

11. Behavior of Light Transparent Translucent Opaque
Light can pass through completely
Translucent
Light is scattered, can still sort of see
Opaque
No light passes through

12. Interaction of Light Can be reflected, absorbed or transmitted
Reflection
Regular-light hits a smooth surface and bounces back, like on a mirror
Diffuse-light hits a rough surface and reflects in many directions, like an ocean
When transmitted can be refracted, polarized, or scattered
Refraction
Angle bends when it hits a new medium
Polarization
Light travels in only one plane, 3D and sunglasses
Scattering
Light hits and is redirected, sunsets

13. Color Dispersion-white light diffracting into rainbow
Color-reflected wavelength is the color, green reflects green light
Primary colors of light
Red, green, blue
Primary colors of pigment
Cyan, magenta, yellow

14. Sources of Light Incandescent Fluorescent
Electrons flow through a filament, get red hot, give off light and heat
Most energy given off as heat, not very efficient
Fluorescent
A phosphor is excited by electricity and emits photons that we see as light
Have mercury vapor in them

15. Sources Continued Laser Light Neon Light
Light amplification by stimulated emission of radiation
Photons are lined up and focused on a specific point, no scattering
Neon Light
Gases are excited by electricity and emit photons at specific wavelengths
Ne (red), He (pink), Kr (purple), Hg-Ar (green)