Type of wave Travel in Vacuum? Speed Speed vs. Medium Light Sound vs. Sound Longitudinal No, Mechanical wave ~340 m/s (in air) 1,100 feet per second More elastic/denser medium = Greater speed of sound Sound travels through all substances Light Transverse Yes, Electromagnetic wave 300 million m/s (in vacuum) 186,000 miles per second Light 1/3 slower in water than in air. Light cannot pass through opaque materials Sensation Produced Variations in Sensations Produced Hearing Low frequency = low pitch note High frequency = high pitch note Seeing Low frequency = red light High frequency = violet light Wave Diagram
What happens to light rays when they hit an object?- Page 2 3.4- THE STUDENT WILL DIFFERENTIATE AMONG REFLECTION, REFRACTION, AND ABSORPTION OF WAVES. [P8C2] When light rays hit an object, they are either: Reflected Absorbed Transmitted (pass through the object) What you see of an object depends on how the surface of it reflects light
Opaque, Transparent, Translucent Lab- Page 3 Different objects allow different amounts of light to pass through them The amount of light that passes through an object can be described as: Transparent Translucent Opaque Page 3- Now, using the diagrams provided, write a hypothesis (IF, THEN, BECAUSE) for transparent, translucent, and
Transparent materials are those that transmit nearly all light through them (allow light to pass through) You can see objects clearly on the other side of a transparent object; no distortion Ex. Windshield glass, air, saran wrap
Translucent materials are those that allow some light to pass through them, while the rest of the light is reflected off of the surface of the object Light is scattered, so you may see the object through the material, but not clearly. Ex. Frosted glass, wax paper
Opaque objects are those that do not allow any light rays to pass through them; they reflect or absorb all light that strikes it You cannot see through them Most objects are opaque Ex. Wood, metal, wool, cotton
Page 2 3.8- THE STUDENT WILL EXPLAIN THAT AN OBJECT IS SEEN WHEN LIGHT REFLECTED FROM AN OBJECT ENTERS THE EYE. [P8C1] Reflection the process of light striking an object and bouncing off
White light from the sun is actually made up of a mixture of colors (ROY G BIV) Parts of objects absorb some wavelengths of light and reflect all others The color black all colors are absorbed no colors are reflected The color white all colors are reflected no colors are absorbed All colors absorbed White Black All colors reflected When light wave from all colors enter the eye at the same time, the brain interprets the color as being white Watch- They Might Be Giants- ROY G BIV
Red The Color Red Reflects: RED Absorbs: Orange, yellow, green, blue, violet Yellow The Color Yellow Reflects: YELLOW Absorbs: Red, orange, green, blue, violet Blue The Color Blue Reflects: BLUE Absorbs: Red, orange, yellow, green, violet
Objects can appear different colors depending on the color of light in which they are seen Ex: Water at sunset Objects seen through filters Color filters only allow certain colors to pass through them, absorbing or reflecting the rest A red filter only allows red light to pass.
Think back to your elementary school art classes to help you answer the following questions! 1. What three colors can you use to make any other color? Red, Yellow, Blue 2. What are these three colors called? Primary Colors (def.) - Three colors that can be used to make any other color 3. What color combinations can
Did You Know? Television, phone, and computer screen pictures are made up of only red, green and blue lights so the images are all produced by varying the Primary Light Colors Red, green, and blue colors, which when combined in equal amounts, produce white light Secondary Light Colors a color produced by two primary colors RED + GREEN = YELLOW RED + BLUE = MAGENTA BLUE + GREEN = CYAN RED + GREEN + BLUE = WHITE
Pigments opaque substances that reflect particular colors; substances used to color other materials Primary Pigment Colors magenta, yellow, cyan colors, which when combined in equal amounts, produce the color black Think of your printer cartridge Secondary Pigment Colors: The color you see is the color of light that particular pigment reflects CYAN + YELLOW = GREEN CYAN + MAGENTA = BLUE YELLOW + MAGENTA = RED CYAN + YELLOW + MAGENTA = BLACK Artists create different shades of colors using paints and dyes of both primary and secondary pigments Colors in print are all made up of various combos of magenta, yellow and cyan
Page 4 Rays of light usually travel in straight lines until they hit something You can see objects because light reflects or bounces off of them. What you see depends on how surface light is reflected from an object. The light that reflects off the surface of an object must reach our eyes in order for us to see it Page 5 Color the fruit Red apple, yellow banana, purple grapes, green pear Color the arrow from the fruit in the color that is reflected! 3.8- THE STUDENT WILL EXPLAIN THAT AN OBJECT IS SEEN WHEN LIGHT REFLECTED FROM AN OBJECT ENTERS THE EYE. [P8C1]
Good reflection Occurs when parallel rays of light hit a smooth surface and all of the rays are reflected at the same angle You can see your reflection from a surface that reflects regularly. Mirror- Glass with a silver coating on one side that reflects light regularly Plane Mirror- smooth, flat Images are upright Images are same size as reflected object Concave Mirror- curves inward Images are enlarged if close Images are up side down if you are far away Convex Mirror- curves outward Light rays spread out and appear to meet at a focal point behind the mirror
Occurs when parallel rays of light hit a smooth or flat surface. All rays are reflected at the same angle. (reflected regularly)
Diffuse reflection (poor reflection) occurs when parallel rays of light hit a bumpy or uneven surface; light rays are reflected in all different angles Allows you to see the object but not your reflection. Most objects reflect light diffusely.
REGULAR REFLECTION DIFFUSE REFLECTION
Ray- Straight line used to represent a light ray Angle of Incidence (i) - The angle at which the ray hits the surface (measured from an imaginary perpendicular line) Angle of Reflection (r) - The angle of the rays bouncing off a surface Law of Reflection - The angle of incidence = angle of reflection Normal - The perpendicular direction to a given surface; the point of reference for measuring angles that hit surfaces Drawn as a dashed line! - - - - - - - -
When a wave moves from one medium to another medium at an angle, it changes speed as it enters the second medium, which causes it to change direction and bend. Refraction- The bending of waves due to change in speed Here this pencil appears to be bent inside the glass of water. How many different pencils do you see?
Minute Physics: Speed of Light in Glass VIDEO 1m41s Light waves travel fastest through gases Light waves travel slower through liquids Light waves are slowed even more as they pass through solids Type of matter Change in Speed What happens? Gas Liquid Fast Slow Light wave bends towards the normal Gas Solid Fast VERY SLOW Light wave bends towards the normal Gas Gas What does it look like? Liquid Solid Liquid Gas Slow Fast Light wave bends away from the normal Liquid Gas Solid Gas VERY SLOW Fast Light wave bends away from the normal Solid Gas
Refract (or bend) light cause white light to separate into its separate wavelengths we see these different wavelengths as COLOR The prism splits white light into its different wavelengths. We see these as COLOR
Transverse waves that have properties of changing electric and magnetic fields The sun is producing an enormous amount of energy all the time. This energy pours off the sun as electromagnetic waves and rays. Different wavelength & frequency = different type of wave Transfer energy called electromagnetic radiation from one place to another Do NOT require a medium to travel Can travel through the vacuum of outer space All EM waves travel at the same speed Speed of light = 300,000,000 m/s
Electromagnetic waves are emitted by the Sun and other stars EM waves all travel at the same speed, but have different wavelengths and frequencies 3.7- THE STUDENT WILL USE AN ELECTROMAGNETIC RADIATION SPECTRUM DIAGRAM TO EXPLAIN THAT THE SUNS ENERGY ARRIVES AS LIGHT WITH A RANGE OF WAVELENGTHS. [P8C1]
Radio Waves- Longest wavelength; Lowest frequency Uses: Television Radio Numbers on your radio tell you what frequency you are listening to! AM Radio Waves Range: 600 200 m FM Radio Waves Range: 5.5 0.187 m Cell Phones Police Radar
Microwaves- radio waves with the shortest wavelengths and the highest frequencies Uses: Heating Food Microwave oven- EM waves bounce around inside the oven, penetrate the food, water molecules inside the food absorb the energy, the food gets hot! Transmit cell phone calls Microwave radiation can pass through certain materials like plastic and glass, but are blocked by metals, which create sparks and even fire as they bounce off so no spoons in the microwave!
Infrared Rays the prefix Infra- in Latin means below, so the name means below red Feel them as heat Invisible to the naked eye Most objects give off infrared rays most important source of infrared radiation is the sun Contributes to the Greenhouse Effect Uses: Heating food Detecting people/animals in dark Ghost hunting Remote controls have an infrared source and your TV has a detector A thermograph of an elephant
Visible Light- the only part of the EM spectrum you can see Called the Visible Spectrum Main source: SUN! Range: 750 400 nm Uses: Each wavelength of EM light shows to our eyes as a different color This visible part of the electromagnetic spectrum consists of the colors that we see in a rainbow. ROY G BIV- Red, Orange, Yellow, Green, Blue, Indigo, Violet Longest wavelengths = red Shortest wavelengths = violet P8C1- Students know visible light is a narrow band within the electromagnetic spectrum. I/S
Ultraviolet Rays the prefix Ultra- in Latin means beyond, so the name means beyond violet Main source: SUN! Uses: Since they have a higher frequency than visible light, they carry more energy Damage or kill bacteria (goggle cabinet!) Small doses provides vitamin D, needed for healthy bones and teeth Used to treat jaundice (yellowing of skin) Tanning Overexposure can burn skin, cause skin cancer or damage your eyes Dentistry- curing seals on teeth Detecting forged banknotes
X-rays- EM waves with very short wavelengths Uses: Can penetrate most matter medicine and airport security. Your doctor uses them to look at your bones and your dentist to look at your teeth. Make images of bones inside the body X-rays pass through skin and soft tissues and cause the photographic film to darken when it is developed Denser matter (lead or bone) absorbs X-rays and does not allow them to pass, so image shows up lighter Airport Security *Too much exposure can cause cancer
Gamma Rays Shortest wavelength, Highest frequency Uses: Carry the greatest amount of energy; are the most penetrating of the EM waves Can cause serious illnesses When used in controlled conditions, can kill cancerous cells in radiation treatments Examine the body s internal structures Objects far out in space emit gamma rays, which must travel billions of years before reaching Earth