Catalyst 1. What’s the difference between kinetic and potential energy? Kinetic energy is moving. Potential energy is stationary but deals with height. They both deal with mass. 2. If you drop a bowling ball and a tennis ball from 5 feet, why will the bowling ball make a dent in the floor while the tennis ball won’t? Don’t they have the same potential energy? The bowling ball has more potential energy because it’s heavier. 3. Find the kinetic energy of a ball weighing 10 kg and traveling at 8 m/s. Ek= 0.5 * 10 * 82= 320 J
Why are leaves green? • Leaves are green because they reflect green light and absorb red and blue light.
prisms Why do colors exist? Scientists use _______ to break light into a spectrum of colors.
The spectrum of visible light is called ROYGBIV: n d i g o i o l e t r a n g e r e e n e l l o w l u e e d Why do colors exist? You can see ROYGBIV in a rainbow! 510 nm 475 nm 590 nm 570 nm 445 nm 400 nm 650 nm wavelengths Different colors of light have different ______________. Wavelengths are measured in ___________________ – 1 billionth of a meter. nanometers (nm)
reflected colors of light Why do colors exist? The light you see is what’s ___________ from an object. Black objects absorball ______________. White objects reflect_________________. all colors of light
green red and blue light Why do colors exist? Leaves are ______ because they absorb all the _________________, which has more energy. They reflect the ___________, because it has very ____________. green light little energy
red light blue light Why do colors exist? Red objects absorb everything but _________. Blue objects absorb everything but _________, etc.
Why do colors exist? 1) A police officer’s blue suit: Blue light is reflected; everything else is absorbed. 2) An astronaut’s orange suit Orange light is reflected; everything else is absorbed. 3) A stop sign Red light is reflected from the sign, but all light is reflected from the word “Stop” 4) A soccer ball All light is reflected from the white pentagons, and all light is absorbed into the black ones.
Absorption & Reflection(We do) 5) You’re part of an interstellar exploratory mission. You land on one of the planets orbiting Alpha Centauri, the closest star to our solar system. There’s life on the planet but all the plants are blue! What can you assume about Alpha Centauri that’s different than the Sun?
Electromagnetic Waves • Wave that can travel through empty space or matter • Consists of changing electric and magnetic fields • Shortened to EM • Produced by vibrations of electrically charged particles
Electromagnetic Spectrum • Divided based on wavelength of the waves • Radio waves - longest EM wave – the basis of all technology and communication devices • Microwaves – shorter than radio – used in microwaves, radar, and communication with satellites
Electromagnetic Spectrum • Infrared – shorter than microwaves – heat. Almost all things radiate heat. Used in infrared photography (for military intelligence) • Visible Light – very narrow range of the spectrum…known as ROY G BIV
Electromagnetic Spectrum • Ultraviolet – produced by the sun – shorter than visible – causes sunburn, but kills bacteria! • X-Rays– very short wavelengths. X-Rays used in medical field – cannot see thru lead (like SUPERMAN).
Electromagnetic Spectrum • Gamma Rays – shortest wave of all. Used in radiation treatment of cancer • Over-exposure to either X-Rays or Gamma Rays is very detrimental to your health.
Absorption and Scattering • Absorption – when light passes through an object and the light is dimmer once it passes thru • Scattering – interaction of light that causes light to change direction. Light scatters in all directions!
What are you talking about??? • When light strikes an object, the light can be reflected, absorbed, or transmitted. • Opaque: an object that absorbs all the light that strikes it – most objects are opaque.
AGAIN… • Transparent: material that transmits light – light passes thru – like glass… • Translucent: material that scatters light – you cannot see thru – like wax paper.
Reflection… • Regular reflection: when parallel rays bounce off a smooth surface • Diffuse reflection: when parallel rays bounce off a bumpy surface
Mirrors… • Image: a copy of an object formed by reflection or refraction • Plane mirror: flat mirror • Concave mirrors or lenses: mirror curved inward • Real image: image is exact • Virtual Image: image is distorted
Mirrors continued… • Convex mirrors or lenses: Surface curves outward • Printed/painted images are virtual
Refraction… • When light enters an object and the direction is changed (like a fish tank) • Index of Refraction: a measure of how much the light is bent. • Prisms: 3-D piece of glass – when light is caught – all the colors of light are displayed
Light… • Rainbows: refracted light thru raindrops • Mirages: image of a distant object caused by refraction
COLOR • The color of an object is the light it reflects • You can change the image by changing the color of light and perhaps adding a filter. • Primary colors of LIGHT: red, blue, green – can be combined to make ANY color • Other colors are called secondary colors
Color continued… • When the primary colors of light are combined in equal amounts – they make white light • Technically, there is no darkness (just like cold doesn’t exist). • So darkness, is simply the absence of light.
Pigments… • Used to color other materials • Opaque substances that reflect color • Very different from light… • As pigments are added together, fewer colors of light are reflected and more are absorbed.
So, what does that mean?? • The more pigment, the darker the color. • Primary pigment colors are: cyan (blue), yellow, and magenta. • Combine any 2 pigments in equal amounts and you get a secondary color. • White is the absence of color. • Black is the combination of all color.
THE EYE!!! • Made of the cornea, iris, pupil, lens, retina, nerves, etc • The cornea – light enters here – protects the eye • The iris – the colored portion • The pupil: looks black – contracts and expands in light
More on the Eye! • Macula: yellow part of retina that gives us vision, without it you’d be blind • Sclera: white, tough wall of the eye that serves to protect and give shape to the eye • Vitreous Humor: jelly-like material that fills the eye – provides shape • Aqueous Humor: water-like material between cornea and lens that gives oxygen and nutrients to the eye
Continued… • The lens: convex lens that refracts light • The retina: cells lining the eyeball - made of rods and cones • Rods: distinguish between black, white, and gray • Cones: see color
One more time… • The optic nerve: sends signals to brain and turns the image right side up. • Glasses (Lenses) : help to correct vision – the eyeball is typically too long or too short • Nearsightedness: can see close up • Farsightedness: can see far away
How do we use it? • Telescopes: use lenses to reflect images from the sky • Microscopes: use lenses to magnify • Cameras: uses lenses to focus • Lasers: Uses light and lenses to direct and intensify – CD’s, Surgery, Holograms, Optical fibers (phone lines), communication, and medicine…