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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)