- Slides: 28
Bill Nye: Light Optics 1. Light energy can: A. bounce B. bend C. be absorbed D. All 2. When light hits a mirror: A. it bends B. it bounces C. it is absorbed D. none 3. A remote control for a television uses: A. electromagnetic radiation B. infrared light C. Invisible energy D. All of the above 4. Concave lenses make things look: A. bigger B. smaller C. blurrier D. closer 5. Optical fibers: A. are used for telephone and computer lines B. send info. with light C. both of these D. None of these
Bill Nye: Light Optics 1. Light energy can: D. All of the above 2. When light hits a mirror: B. It bounces 3. A remote control for a television uses B. Infrared Light 4. Concave lenses make things look: B. Smaller 5. Optical fiber C. Both of the above
What is Light? • Turn to page 1 in your books • Let’s make a list of things that give us light. • How many could we think of?
What is Light? • • Light is a form of ENERGY that you can SEE. Light is one kind of RADIANT ENERGY. Light comes from MANY different SOURCES. Some items PRODUCE light, while others REFLECT light. • Is it a producer or a reflector? – – – Candle Mirror Sun Flashlight Jupiter • What are 4 other things that produce light? • What are 4 other things that reflect light?
Think About It • Where do you sit when you watch television? WE SIT IN FRONT OF IT. • Let’s look at the laser pointer • How does it travel? Circular? Crooked? In a straight line? THE LASER LIGHT TRAVELS IN A STRAIGHT LINE. • So, how does light travel? • Light TRAVELS in a STRAIGHT LINE. • What other real life examples have light that travel in a straight line? • How is this different than how sound travels?
Light Experiments • Let’s turn to page 3 • We have different light sources, and we know that not all light sources are the same. • Let’s compare and contrast our different light sources.
Reflection (page 4) • Light can be REFLECTED or ABSORBED by a surface. • When light is REFLECTED, it BOUNCES OFF that surface. - Example: A MIRROR • When light is ABSORBED, it is TRAPPED by that surface. - Example: BODY • Light is REFLECTED of a surface in a special way.
Basketball Demonstration • I need 2 volunteers. • I’m going to have them bounce pass the basketball to one another. • Picture an imaginary line made by the basketball as it travels to the ground, it hits the floor, and the imaginary line made as it bounces back up. • Now they are going to move a little closer. Picture the imaginary line again. • Now they are going to move farther apart. Picture the imaginary line. • Do you see a different line? • What if I bounced the ball directly down? • Let’s log our observations.
Page 5 • The TENNIS BALL and the BASKETBALL actually represent what happens to LIGHT as it is REFLECTED. • When LIGHT hits a REFLECTIVE surface, like a MIRROR, it will BOUNCE BACK at the SAME ANGLE. • The angle at which light STRIKES A SURFACE is the ANGLE OF INCIDENCE. • The angle at which light REFLECTS OFF a surface is the ANGLE OF REFLECTION. • The angle of incidence is › ‹ = the angle of reflection. • Example: When LIGHT strikes a MIRROR at a 45º angle, it is reflected at a 45º angle.
Textbook Reflection Activities • Can we use what we know about the angle of incidence and the angle of reflection to move light? • Turn to page 6, let’s see if we can get the light to move from one side of a textbook to the other only using the textbook, light, and mirrors. • Let’s draw our solution.
Laser and Mirrors Activity (Lab Day) • I’ve got a laser. • I’m going to pass out a few mirrors. • Let’s see if we can get the laser to travel across the classroom.
Mirrors That Multiply • Turn to page 7 • We are going to test different angles on a hinged mirror to see what happens.
Reflection Experiment • Turn to page 8 in your books. • We know light reflects off a mirror • Is a mirror the only thing that can reflect light? • Let’s experiment with different surfaces to see if they will reflect light.
Reflected, Absorbed, or Transmitted? • Light that PASSES THROUGH matter is TRANSMITTED by the material. • If light is not TRANSMITTED, some of it is REFLECTED. • If light is not TRANSMITTED or REFLECTED, it is ABSORBED. • There are 3 types of materials: • Transparent: LIGHT IS TRANSMITTED (PASSES THROUGH). • Translucent: SOME LIGHT IS TRANSMITTED, SOME IS REFLECTED AND SCATTERED. • Opaque: LIGHT IS ABSORBED (NOT TRANSMITTED).
Transparent, Translucent, or Opaque • Let’s categorize our items (page 9): Transparent Translucent Opaque
Refraction • What do we observe with a thumb or a pencil in a cup of water? • Let’s illustrate our observation • When an object is placed in a glass of WATER it appears to be BROKEN. This is because of light REFRACTION. • Light changes DIRECTION when it enters a new MEDIUM. • A medium is any SUBSTANCE through which a WAVE is TRANSMITTED. • LIGHT is traveling from the overhead light bulbs through AIR. When the LIGHT enters the cup of WATER, it enters a new MEDIUM. This causes the LIGHT to change DIRECTION. • Light in AIR travels FAST. • Light in WATER travels MORE SLOWLY. • When light SLOWS DOWN, it changes DIRECTION. • When light changes DIRECTION or BENDS, it is called REFRACTION. • REFRACTION is caused by the change of the SPEED OF LIGHT as it travels through different MEDIUMS.
Speed of Light • The speed of light is 186, 000 MILES PER SECOND • That is the same as 7 ½ TIMES AROUND THE EARTH IN ONE SECOND. • This is how fast light travels in AIR. When it enters a new MEDIUM (like water), it slows down. The result is REFRACTION.
Appearing Coin • Look at the cup from the side so you can still see the bottom of the inside of the cup, but you cannot see the coin glued to the bottom. • Slowly pour water into the cup until you see the coin appear. • Why does it work? • THE COIN DIDN’T MOVE. THE CUP DIDN’T MOVE. THE WATER CAUSED THE LIGHT TO BEND AND MADE THE COIN VISIBLE. IT’S REFRACTION!
Color of Light (page 12) • Light TRAVELS in WAVES. • Let’s draw and label a light wave. • FREQUENCY is the measure of the number of WAVES that pass by a given point in one second. • Remember, LIGHT is one kind of RADIANT energy. • Radiant energy includes WAVES of all different WAVELENGTHS and FREQUENCIES. • When all the types of RADIANT ENERGY are arranged in ORDER, we have the ELECTROMAGNETIC SPECTRUM. • http: //imagine. gsfc. nasa. gov/science/toolbox/emsp ectrum 1. html • Let’s draw and label the Electromagnetic
Visible Light (page 13) • We can only see one portion of the electromagnetic spectrum. That portion is called VISIBLE LIGHT. • What color is the light from most light bulbs? WHITE. • Although we see WHITE light, it’s actually made up of many COLORS. • The colors of the spectrum are: red, orange, yellow, green, blue, [indigo], violet • An easy way to remember these colors in order is: ROY G. Bi. V
ROY G. Bi. V drama • Newton divided the spectrum into seven named colors: red, orange, yellow, green, blue, indigo, and violet. He chose seven colors out of a belief, derived from the ancient Greek sophists, of there being a connection between the colors, the musical notes, the known objects in the solar system, and the days of the week. The human eye is relatively insensitive to indigo's frequencies, and some otherwise-well-sighted people cannot distinguish indigo from blue and violet. For this reason, some later commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right but merely as a shade of blue or violet.
Prism Glasses (Lab Day)
Prisms (page 13) • Prisms separate light into the colors of the spectrum. Let’s use a prism and a flashlight to see if we can create a rainbow. What technique seemed to work best? • SHINING A LIGHT ON AN EDGE • Is a prism the only way we see a rainbow? NO. • When do you usually see a natural rainbow? AFTER RAIN. • How was that rainbow created? What caused the sunlight separate? • THE WATER VAPOR LEFT IN THE AIR AFTER A RAIN STORM ACTIS AS A PRISM TO SEPARATE THE LIGHT.
Blending Light (page 14) • We can use a prism to separate the colors of white light, so we can see all the colors of the spectrum. Is it possible to blend the colors of light and make white? Let’s find out. We need 3 flashlights and red, green, and blue cellophane. • Record your observations • RED + GREEN + BLUE = WHITE LIGHT • https: //www. youtube. com/watch? v=ks. SFJ 3 B 8 Og golf ball to white
Colors (page 14) • If light is made of all the colors of the spectrum, how do we see certain colors? Why do we see white, black, or red? • Let’s illustrate what happens. • Why we see white: ALL THE COLORS STRIKE, ALL COLORS ARE REFLECTED • Why we see black: ALL COLORS STRIKE, ALL COLORS ARE ABSORBED • Why we see red: ALL COLORS STRIKE, RED REFLECTED, THE REST ARE ABSORBED • https: //www. youtube. com/watch? v=APCe. EFs. WI watch at 14: 00 minutes • https: //www. youtube. com/watch? v=gtg. BHs. Sz. CPE Bill Nye, minutes 1 -4
• https: //www. youtube. com/watch? v=c 5 v 377 er. Ikc Brain Games dot/color phenonomena • https: //www. youtube. com/watch? v=Cbka. Lvgi. KI Mirrors and Light song Mr. Parr