Table of Contents Preview 2.1 Waves and the Electromagnetic Spectrum 2.2 Visible Light and Color 2.3 Reflection and Refraction 2.4 Seeing Light 2.5 Optical Tools
Preview Questions 1. What causes a building to cast a shadow in sunlight? a. The building is very dark. b. The building blocks the sun s light. c. The building s windows capture the light. d. The building gives off rays of darkness.
Preview Questions 1. What causes a building to cast a shadow in sunlight? a. The building is very dark. b. The building blocks the sun s light. c. The building s windows capture the light. d. The building gives off rays of darkness.
Preview Questions 2. When light hits a mirror, it a. passes through the mirror. b. bounces back to where it came from. c. reflects off the mirror. d. curves around it.
Preview Questions 2. When light hits a mirror, it a. passes through the mirror. b. bounces back to where it came from. c. reflects off the mirror. d. curves around it.
Preview Questions 3. If a red light shines on a white piece of paper, the paper will appear a. red. b. blue. c. green. d. yellow.
Preview Questions 3. If a red light shines on a white piece of paper, the paper will appear a. red. b. blue. c. green. d. yellow.
Preview Questions 4. Why can t you see a friend who hides behind a tree? a. The tree reflects your friend s light back. b. The tree s leaves cast a shadow on your friend. c. The tree absorbs all the light that hits it. d. The tree blocks the light from your friend from reaching your eyes.
Preview Questions 4. Why can t you see a friend who hides behind a tree? a. The tree reflects your friend s light back. b. The tree s leaves cast a shadow on your friend. c. The tree absorbs all the light that hits it. d. The tree blocks the light from your friend from reaching your eyes.
End of Preview
How does light allow you to see? Suppose you aim a flashlight at a pair of colored light filters. The first filter is blue and the second one is red. When the light passes through the blue filter, it will emerge blue. But what happens when the blue light passes through the red filter?
Latin Word Origins Latin Word flectere Meaning of Latin World to bend Key Term reflection The bouncing back of something, such as light or sound, when it hits a surface
Latin Word Origins Latin Word lu, lucere Meaning of Latin World to light Key Term translucent Scattering light; allowing some, but not all, light to pass through
Latin Word Origins Latin Word re- Meaning of Latin World back; again Key Term reflection The bouncing back of something, such as light or sound, when it hits a surface
Latin Word Origins Latin Word trans- Meaning of Latin World through; across Key Term transparent Allowing light to pass through
Apply It! 1. Which key term in the chart comes from the two Latin words flect and re? How does the meaning of this key term involve both those Latin words? reflection; it is the bending back of light so it returns or comes back 2. What part of the word translucent lets you know that the word s meaning has something to do with light? lucent; from the Latin Lucere, meaning to light
Section 1: Waves and the Electromagnetic Spectrum What causes waves? What are the basic properties of waves? What does an electromagnetic wave consist of? What are the waves of the electromagnetic spectrum?
Electromagnetic Waves We are :showered all the time by waves.- disturbances that transfer (move) energy from place to place. Waves carry energy. Energy: the ability to do work. Think about the energy you are using right now!
Mechanical vs. Electromagnetic Waves How are light like ocean waves? They have similar shapes. They both carry energy! (Think about it: they can both DO things! How?
Mechanical vs. Electromagnetic Waves How are light different than ocean waves? Ocean waves move through a medium (a material through which things travel). Mediums can include solids, liquids, and gases. What medium do ocean waves travel through? Wave that must move through mediums are called mechanical waves. Light waves are a type of electromagnetic wave- (waves made of electric and magnetic fields).
Electromagnetic Waves What kinds of mediums must EM waves travel through? Trick question: None! Though they can travel in mediums, Electromagnetic waves are unique because they can travel in a vacuum- like outer space- where there is no medium! Are sound waves electromagnetic or mechanical waves?
Wave Vibration Mechanical waves (waves that move through mediums) are produced when energy causes a medium to vibrate- bounce back and forth on the particle (atomic) level
Wave Properties: #1 Amplitude Amplitude: maimum distance that the particles in a medium move away from their resting spot. Crest: high point Trough: Low point Amplitude What units are used to measure amplitude?
Wave Properties: #1 Amplitude Amplitude: maimum distance that the particles in a medium move away from their resting spot. Crest: high point Trough: Low point Amplitude
Wave Properties: #1. Amplitude Amplitude: maimum distance that the particles in a medium move away from their resting spot. Crest: high point Trough: Low point If a wave has a smaller crest than another wave, would it have a smaller or larger amplitude? Do the wave: Can we change the amplitude?
Wave Properties: #2. Wavelength Wavelength: the distance between two corresponding (matching) parts of the wave Why can't we measure the wavelength from two resting positions? Which moves with more energy: waves with shorter or longer wavelength? What are the units used to measure wavelength? Do the wave: Can we change the wave length?
Wave Properties: #3. Frequency Frequency: the number of complete waves that pass a given point in a certain amount of time Hertz: units of frequency (per second!) (#/s) If a wave has a frequency of 1 Hz, it moves at one wave passing the same point every second What is the frequency of a wave in which two complete waves pass a given point every second? What are the units of frequency? Do the wave! Can we change the frequency?
Wave Properties: #4. Speed Speed: How far the wave travels in a given amount of time Speed = distance/time (m/s) Speed = Wavelength (distance) X Frequency (/second) Speed increase if you increase frequency or wavelength! What are the units? Do the wave! Can we change the speed?
Angles An angle is formed when two lines meet at a point. Angles are measured in degrees, indicated by the symbol º. A circle has 360 degrees. A right angle is an angle that contains 90 degrees. Two lines that meet at a point to form a 90º angle are said to be perpendicular to each other.
Angles Practice Problem Draw a circle on a piece of paper. How many right angles can you fit in the circle? Four right angles can fit in a circle.
What Is an Electromagnetic Wave? Electromagnetic wave -vibrating electric and magnetic fields moving through space at the speed of light. When charged particles move, they create magnetic fields (magnetic pushes/pulls). This in turn creates an electric field (electron flow) that moves at right angles to the pushes/pulls of the magnetic field. This creates an electromagnetic wave! What does the long arrow in the figure represent? In what direction does the wave travel relative to the vibrations?
What Is an Electromagnetic Wave? Electromagnetic radiation: Energy in space carried by electromagnetic waves! They move at the speed of light: 186,000 mi/s or 300,000 km/s! It takes 8 minutes at that speed for the electromagnetic waves from the sun (our light!) to reach the earth! Thick mediums can slow it down, but in outer space (a vacuum), there is no medium! Weird and ground-breaking stuff: http://www.reuters.com/article/2011/09/23/us-science-light-idustre78l4fh20110923
What Is the Electromagnetic Spectrum? Electromagnetic spectrum complete range of electromagnetic waves in order of increasing frequency. Visible Light: The light that you can see! All the other EM waves are invisible. Which of these types of waves have you heard of before? Where is visible light on the EM Spectrum? What types of waves have longer/shorter wavelengths?
What Is the Electromagnetic Spectrum? Fun stuff (Just note eamples!) Radio Waves: AM/FM, Television- longests/ slowest waves AM are longer waves,travel better over farther distances (and hills) Radio Waves can be up to a mile long! What Hertz is your favorite station? Wavelength = speed of light/frequency KKIQ: (101.7 MHz) would have a wavelength of about 3 meters. 300,000 m/s divided by 101700 waves/second =2.9 m
What Is the Electromagnetic Spectrum? Fun stuff (Just note eamples!) Microwaves: Radio waves with shortest wavelength & highest frequency (fast radio waves) -radar, cell phones, Microwave ovens work by heating the water molecules in food Waves the size of house flies (metal grid in glass in door stops mw) Infrared Rays: invisible rays, found in heat lamps Why do heat lamps glow red if infrared rays are invisible? night goggles (convert IR to an image), remote controls Waves are the size of a pinpoint
What Is the Electromagnetic Spectrum? Fun stuff (Just note eamples!) Visible Light: The part you can see (only a small part of light!) the colors of the rainbow (ROYGBIV) Waves are 800 nm (.0000008m) for red to 400 nm for violet Ultraviolet rays: Higher energy, UVA, UVB, UVC in sunlight Used in crime scenes and black lights With black lights, are we really seeing black light? Can cause cancer but also needed to make vitamin D Blocked by sunscreen Waves are about the size of bacteria
What Is the Electromagnetic Spectrum? Fun stuff (Just note eamples!) X-rays: used in medical diagnostics because transmitted through skin but absorbed by bone and lead Waves are the size of atomswhy can ecessive X-ray eposure cause cancer? Gamma rays: Shortest wavelength, highest energy Huge amounts of radiation, found in nuclear reactions, including in stars Blocked/absorbed by our atmosphere Why would gamma rays be used in cancer treatment? Waves are the size of an atomic nucleus
Electromagnetic Waves Activity Click the Active Art button to open a browser window and access Active Art about electromagnetic waves.
Links on the Nature of Waves Click the SciLinks button for links on the nature of waves.
Electromagnetic Waves Click the Video button to watch a movie about electromagnetic waves.
End of Section: Waves and the Electromagnetic Spectrum
Section 2: Visible Light and Color How does visible light interact with an object? What determines the color of an opaque object? How is miing pigments different from miing colors of light?
When Light Strikes an Object Light can be: 1. Reflected: bounces off object in another direction 2. Transmitted: travels through object 3. Absorbed: travels into object but not through object Objects can do more than one of these at the same time!
When Light Strikes an Object Mediums can be: 1. Transparent- transmits most of the light that strikes it, can scatter light, esp. if impure 2. Translucent-scatters light, creates a blurry view of the other side 3. Opaque- reflects or absorbs all the light that strikes it Can you think of eamples of each? What happens when light strikes each of these types of objects?
The Color of Objects The color of an opaque object is the color of the light it reflects. Why does the apple appear red and the leaf appears green?
The Color of Objects The color of a transparent object is the color of the light it transmits. Incoming White light Outgoing blue light Why does blue glass appear blue? (Why does a blueberry appear blue and how is this different?)
The Color of Objects The color of an opaque object is the color of the light it reflects. Why does the apple turn black in the absence of red light? Why is the apple red in regular light?
Combining Colors Primary colors: The three colors that can combine to produce all other colors Secondary colors: Created by combining two primary colors in equal amounts How do the primary colors of light differ from the primary colors of pigment?
Combining Colors The primary colors of light combine in equal amounts to form white. (All the wave lengths ADD together to create the whole spectrum, which gives off white light!) Primary Colors of Light: Red, Blue, and GREEN Secondary Colors of Light: Magenta, Cyan (funky blue), and Yellow Which two colors combine to form magenta? Yellow?
Combining Colors The primary colors of pigments combine in equal amounts to form black. All these colors combine together to block more and more colors from being reflected- creating black: all colors are absorbed! The more pigments added together, the less reflection and the more absorbtion. Primary colors of pigments: Magenta, Yellow, Cyan Secondary Colors of pigments: Red, Blue, Green Which two colors combine to form green? Blue?
Combining Colors Light: All the colors add together to create white light! Pigment: All the colors add together to absorb all colorscreating black.
Combining Colors Complementary Colors of Light- when a primary and a secondary color combine to create white light Complimentary Colors of Light: Yellow and blue Cyan and red Magenta and green http://www.brainpop.com/science/energy/color/
Links on Colors Click the SciLinks button for links on colors.
Color Click the Video button to watch a movie about color.
End of Section: Visible Light and Color
Section 3: Reflection and Refraction What does the law of reflection state? Why do light rays bend when they enter a new medium at an angle? What determines the types of images formed by conve and concave lenses? http://www.brainpop.com/science/energy/light/
Reflection Reflection: When an object or wave hits a surface through which it cannot pass, it bounces back. Normal: a line drawn perpendicular to the surface at the point where the incoming wave strikes (hits) Angle of Incidence: Angle between the incoming wave & the normal What does perpendicular mean? What is the approimate angle of incidence in this photo?
Reflection When an object or wave hits a surface through which it cannot pass, it bounces back. Angle of Reflection: angle between reflected wave and the normal line Law of Reflection: Angle of incidence = angle of reflection ANGLE IN = ANGLE OUT If a wave has an angle of incidence of 30 degrees, what would the angle of reflection be?
Plane Mirrors Plane mirror: smooth sheet of glass with silver-colored coating on one side that reflects light Image: copy of an object formed by reflected or refracted light Virtual Image: An image behind the mirror What is a virtual reality game? How is that like a virtual image? Can you think of eamples of images we see? Are any of these virtual images? What does your image in a regular (plane) mirror look like?
Plane Mirrors Plane mirror: smooth sheet of glass with silvercolored coating on one side that reflects light What are the images in plane mirrors like? Plane mirrors create upright, virtual images of the same size as the object. However, left and right are reversed.
Concave Mirrors Concave mirror: surface curves inward like the inside of a bowl or the hollow of a cave. Optical ais: imaginary line dividing the mirror in half Focal point: point at which rays meet or converge Location of focal point depends on mirror shape: The more curved the mirror, the closer the focal point is to the mirror. Bowl of water demo? Why do the light rays change direction? What are eamples of concave mirrors?
Concave Mirror Eamples Beauty magnifying mirrors and reflecting telescopes are eamples of concave mirrors.
Concave Mirrors Concave mirrors can form either virtual images or real images. IN A CONCAVE LENS, THE POSITION OF THE OBJECT RELATIVE TO THE MIRROR AND THE FOCAL POINT MATTERS! CLOSER THAN FOCAL POINT Virtual image: image that appears to be behind the mirror Where is the focal point on a concave mirror? Where is the object in relation to the focal point and mirror? Is this like the beauty mirror or the reflecting telescope?
Concave Mirrors Concave mirrors can form either virtual images or real images. Farther and much farther than focal point Real image: forms when rays meet, found in front of the mirror! How is this different from the earlier image of concave mirrors? (Hint: Where is the object in relation to the focal point and mirror? When does a concave mirror produce a real image? Is this like the beauty mirror or the reflecting telescope?
Concave Mirrors Concave mirrors can form either virtual images or real images. Closer than FP Farther than FP How are these images different? What kind of images can concave mirrors form? Telescope, bowl, and beauty mirror demo Much farther than FP
Conve Mirrors Conve mirror: mirror with a surface curving outward What are some eamples of conve mirrors?
Eamples of Conve Mirrors Security mirrors, rear view mirrors, the back sides of shiny spoons and bowls, and garden globes are eamples of conve mirrors! What are security mirrors, garden globes, and rear view mirrors good for?
Eamples of Conve Mirrors A garden bowl is a conve mirror. What happens to the image in the globe?
Eamples of Conve Mirrors The Chicago Bowl is a giant conve mirror. What happens to the images of the people?
Conve Mirrors Conve mirror: mirror with a surface curving outward Where is the focal point ALWAYS going to be on a conve mirror? What happens to the rays in a conve mirror? What kind of image will this ALWAYS produce?
Conve Mirrors Conve mirror: mirror with a surface curving outward Where is the focal point ALWAYS going to be on a conve mirror? What happens to the rays in a conve mirror? What kind of image will this ALWAYS produce?
Conve Mirrors What kind of images do conve mirrors always create?
Summary
Summary Plane Concave Conve
Summary Plane Concave Conve Virtual Upright Left/right reversed Same size
Summary Plane Concave Virtual Upright Left/right reversed Left/right reversed Same size Larger- close or smaller if very far away Conve Concave: Virtual/Upright if image is closer than FP, Real/inverted if farther than FP
Summary Plane Virtual Concave Conve Virtual Upright Left/right reversed Left/right reversed Left/right reversed Same size Larger- close or smaller if very far away Always smaller Concave: Virtual/Upright if image is closer than FP, Real/inverted if farther than FP
What type of mirror is this?
What's going on here? Which are conve and concave mirrors? Why are they all smaller?
Mirrors Activity Click the Active Art button to open a browser window and access Active Art about mirrors.
Refraction of Light Light travels in a straight line: a. in a vacuum b. when it stays in the same medium c. it his a new medium at a perpendicular angle Light changes direction: a. when it enters a new medium at an angle Refraction: bending of light waves caused by a change in speed
Refraction of Light Light travels at different speeds through different mediums. When light enters a medium at an angle, the change in speed causes the light rays to bend (change direction). Refraction: bending of light waves caused by a change in speed
Bending Light The inde of refraction of a medium is a measure of how much light bends as it travels from air into the medium. The greater the inde of refraction, the slower light travels/more it bends. The table shows the inde of refraction of some mediums. Which medium has the greatest refraction inde? Which generally bend more: solids or liquids?
Bending Light Interpreting Data: Which medium causes the greatest change in the direction of a light ray? Diamond causes the greatest change in the direction of a light ray traveling from air.
Bending Light Interpreting Data: According to the table, which tends to bend light more: solids or liquids? According to the graph, most solids bend light more than liquids do (quartz is an eception).
Bending Light Predicting: Would you epect light to bend if it entered corn oil at an angle after traveling through glycerol? Eplain. You would not epect light to bend if it entered corn oil at an angle after traveling through glycerol, because corn oil and glycerol have the same value for the inde of refraction.
PRISMS Why does a prism split light? The angle of refraction is different for each color or wavelength. The different colors take longer to travel through and come out at different spots! Longer wavelengths (red light) are refracted the most! Shorter wavelengths (violet light) are refracted the least. How is this like the spectroscope?
Rainbows How are rainbows like prisms? White light from the sun is split apart When it hits water droplets. The drops are like the prisms. http://www.brainpop.com/science/energy/rainbows/preview.weml
Pencil in Water What are the two mediums the Light hitting the pencil travels through? Why does the pencil seem to bend? Which medium has a higher refraction inde?
Pencil in Water The water has a higher refraction inde than the air. The pencil bends because light Travels more slowly through water than air. What would happen if we put the pencil in a different liquid? What would happen if the liquid had a higher refraction inde (ie: corn oil)?
Lenses Lens- a curved piece of glass or other transparent material that refracts light What are some eamples of lenses? Do lenses make images with reflection or refraction? Lens shape and the position of the object affect the type of image that results. Where have we heard that before?
Conve lenses How are conve and concave lenses different? Conve lens- thicker in the center than at the edges (bulge out) Concave lens- thinner in the center than at the edges (caves in) What are some eamples of Conve lenses?
Conve lenses What are some eamples?
Conve Lenses An object s position relative to the focal point determines whether a conve lens forms a real image or a virtual image. Closer = virtual, enlarged
Conve Lenses An object s position relative to the focal point determines whether a conve lens forms a real image or a virtual image. Closer = virtual, enlarged Farther = Real, inverted What changes the type of image created? How does the curved surface affect the transmission of light?
Lenses Concave lens- produces only virtual images because parallel light rays passing through the lens never meet. What kind of image does a concave lens ALWAYS produce? How does the curved surface affect the transmission of light/images?
What is the difference between conve and concave here? Where would the focal points of each lens be?
Summary Chart: Lenses Kind of Lens Description Image formed: Real or Virtual? Thinner at the Center than at the Edges Conve Real or virtual
Summary Chart: Lenses Kind of Lens Description Concave Thinner at the Virtual Center than at the Edges Conve Image formed: Real or Virtual? Real or virtual
Summary Chart: Lenses Kind of Lens Concave Conve Description Image formed: Real or Virtual? Thinner at the Virtual Center than at the Edges Thicker at the Real or virtual Center than at the Edges
More complicated Lenses! We only study biconcave and biconve lenses, but there are many combinations. Eye glasses are often meniscus lenses, or concave on one side and conve on the other! Can you find the meniscus lens in the photo?
Lenses Activity Click the Active Art button to open a browser window and access Active Art about lenses.
End of Section: Reflection and Refraction
Section 4: Seeing Light How do you see objects? What types of lenses are used to correct vision problems? http://www.brainpop.com/health/bodysystems/eyes/
Vision You eyes respond to the stimulus of light. They convert that stimulus into impulses that your brain interprets, enabling you to see.
The Eye: Structure and Function You eyes respond to the stimulus of light. They convert that stimulus into impulses that your brain interprets, enabling you to see. Cornea-protects eye & focuses light rays What key idea of life science are we using here?
The Pupil and Iris Pupil: Opening through which light enters Iris: colored ring of muscle surrounding the eye What is the color of everyone's pupil? Why? (Think about what we know about color!) Which of these things epands/contracts in different strengths of light? Why? What color is the iris in animals/people who lack pigment (organisms with albinism)?
Irises without Pigmentation Why is the iris pink in organisms with albinism? Hint: The iris is a muscle!
Retina You eyes respond to the stimulus of light. They convert that stimulus into impulses that your brain interprets, enabling you to see. Retina-layer of cells that line the eye Where does the image form in the eye?
Interpreting Images: Rods and Cones Rods: contain pigments that respond to light and dark Cones: respond to red, blue, or green light
When One Type of Rod Doesn't Work: People who are color blind have one type of cone that doesn't work well. They just don't see as many colors as others, but they do see color! Eample of viewpoint Boys are far more likely to be color-blind than girls.
Lens: bends light rays as they come into the eye and focuses them on the retina. What kind of lens is this? Why is it upside down? This activates the rods and cones, which send signals to the optic nerve. Optic nerve: carries Why don't we see upside down? messages to the brain
Virtual Dissection of the Eye Activity http://www.brainpop.com/health/diseasesinjuriesandconditions/visionproblems/ Click the Active Art button to open a browser window and access Active Art about dissecting an eye.
Correcting Vision Concave lenses are used to correct nearsightedness. Why does a concave lens fi the problem?
Correcting Vision Conve lenses are used to correct farsightedness. Why does a conve lens fi the problem?
More on Eyesight http://www.brainpop.com/science/energy/rainbows/ Click the PHSchool.com button for an activity about eyesight.
End of Section: Seeing Light
Section 5: Optical Tools How are lenses used in cameras, telescopes, and microscopes? http://www.brainpop.com/technology/scienceandindustry/telescopes/ http://www.brainpop.com/technology/scienceandindustry/cameras/
Optical Instruments The lens of the camera focuses light to form a real, upsidedown image on film in the back of the camera. What kind of lens is this? What does the lens do to the image?
Optical Instruments A telescope forms enlarged images of distant objects. Telescopes use lenses and mirrors to collect and focus light from distant objects. How are reflecting and refracting telescopes different?
Optical Instruments Microscope- uses a combination of lenses to produce and magnify an image. Objective lens- gathers incoming Light from the object Eyepiece- magnifies image Is this an electron or light microscope? How can you tell? What kind of lenses are used in microscopes? What do these lenses do to the light?
Magnification vs. Resolution Magnification- ability to make things look larger than they are Resolution-ability to clearly distinguish individual parts of an object (sharpness) Which images have greater magnification or resolution? How do you calculate magnification?
Electron Microscope Electron Microscope: use a beam of tiny particles called electrons instead of light to produce a magnified image What does the increased resolution of an electron microscope allow it to do?
Images: Light vs. Electron Microscopes Fly eye Pollen Microscopic Worm & Bacteria Spinach Cells Which image comes from which type of microscope? Hint: Use L. Acidophilus Chains resolution!
End of Section: Optical Tools
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