KEY CONCEPT Light waves interact with materials

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Page 2 of 7,How Materials Transmit Light, Materials can be classified according to the amount and type of light. they transmit, 1 Transparent trans PAIR uhnt materials allow most of the light. that strikes them to pass through It is possible to see objects. through a transparent material Air water and clear glass are trans. parent Transparent materials are used for items such as windows. light bulbs thermometers sandwich bags and clock faces. 2 Translucent trans LOO suhnt materials transmit some light but. they also cause it to spread out in all directions You can see light. through translucent materials but you cannot see objects clearly. through them Some examples are lampshades frosted light bulbs. frosted windows sheer fabrics and notepaper, 3 Opaque oh PAYK materials do not allow any light to pass. through them because they reflect light absorb light or both. Heavy fabrics construction paper and ceramic mugs are opaque. Shiny materials may be opaque mainly because they reflect light. Other materials such as wood and rock are opaque mainly. because they absorb light, check your reading What is the difference between translucent and opaque materials. This stained glass window,contains transparent,translucent and opaque.
1 translucent,transparent 2,574 Unit 4 Waves Sound and Light. Page 3 of 7, A light filter is a material that is transparent to some kinds of light. and opaque to others For example clear red glass transmits red light but. absorbs other wavelengths Examples of light filters are the colored cov. ers on taillights and traffic lights infrared lamp bulbs and UV protected. sunglasses Filters that transmit only certain colors are called color filters. Scattering, Sometimes fine particles in a material interact with light passing. through the material to cause scattering Scattering is the spreading. out of light rays in all directions because particles reflect and absorb. the light Fog or dust in the air mud in water and scratches or smudges. on glass can all cause scattering Scattering creates glare and makes it. hard to see through even a transparent material Making the light. brighter causes more scattering as you might have noticed if you have. ever tried to use a flashlight to see through fog,Fine particles such as. those in fog scatter,light and reduce visibility, Scattering is what makes the sky blue During the middle of the SUPPORTING MAIN IDEAS.
day when the Sun is high in the sky molecules in Earth s atmosphere Be sure to add to your. chart the different, scatter the blue part of visible light more than they scatter the other ways light interacts. wavelengths This process makes the sky light and blue It is too bright with materials. to see the faint stars beyond Earth s atmosphere At dawn and dusk. light from the Sun must travel farther through the atmosphere before it. reaches your eyes By the time you see it the greens and blues are scat. tered away and the light appears reddish At night because there is so. little sunlight the sky is dark and you can see the stars. check your reading How does scattering make the sky blue. Chapter 17 Electromagnetic Waves 575,Page 4 of 7,Polarization. Polarizing filters reduce glare and make it easier to see objects. Polarization POH luhr ih ZAY shuhn is a quality of light in which. all of its waves vibrate in the same direction Remember that. EM waves are made of electric and magnetic fields vibrating at right. angles to each other Polarization describes the electric fields of a light. wave When all of the electric fields of a group of light waves vibrate. in the same direction the light is polarized, Light can be polarized by a particular type of light filter called. a polarizing filter A polarizing filter acts on a light wave s electric. field like the bars of a cage The filter allows through only waves. whose electric fields vibrate in one particular direction Light that. passes through the filter is polarized In the illustration below these. waves are shown in darker yellow,Light reflecting off the surface. of this pond causes glare,unpolarized light waves,The fields of visible light waves.
vibrate in all directions,polarized light waves,A polarizing filter lets through. only waves vibrating vertically,no light waves,A second filter lets through only. A polarizing filter reduces waves vibrating horizontally. glare making it possible to,see objects under the water. What do you think happens when polarized light passes into a. second polarizing filter If the direction of the second filter is the. same as the first then all of the light will pass through the second fil. ter The light will still be polarized If the second filter is at a right. angle to the first as in the illustration above then no light at all will. pass through the second filter,Wavelengths determine color. The section of the EM spectrum called visible light is made up of. many different wavelengths When all of these wavelengths are. present together as in light from the Sun or a light bulb the light. appears white,576 Unit 4 Waves Sound and Light,Page 5 of 7.
Seen individually different wavelengths appear as different. colors of light This fact can be demonstrated by using a. prism A prism is a tool that uses refraction to spread out the. different wavelengths that make up white light The prism. bends some of the wavelengths more than others The. lightwaves bent at slightly different angles form a color. spectrum The color spectrum could be divided into countless. individual wavelengths each with its own color However the. color spectrum is usually divided into seven named color. bands In order of decreasing wavelength the bands are red. Prisms split light into, orange yellow green blue indigo and violet You see a color colors by refracting. spectrum whenever you see a rainbow wavelengths in different. Color Reflection and Absorption, The color of an object or material is determined by the wavelengths it. absorbs and those it reflects An object has the color of the wavelengths. it reflects A material that reflects all wavelengths of visible light appears. white A material that absorbs all wavelengths of visible light appears SUPPORTING MAIN IDEAS. Describe the roles of, black A green lime absorbs most wavelengths but reflects green so reflection and absorption. the lime looks green as shown below in color,1 In this simplified 2 3. The lime absorbs The lime reflects, diagram light of all wavelengths mostly green so it.
all colors strikes except green appears green, The color that an object appears to the eye depends on another. factor besides the wavelengths the object absorbs and reflects An. object can reflect only wavelengths that are in the light that shines on. it In white light a white object reflects all the wavelengths of visible. light and appears white If you shine only red light on a white piece of. paper however the paper will appear red not white because only red. light is available to be reflected, In summary two factors determine the color of an object first the. wavelengths that the object itself reflects or absorbs and second the. wavelengths present in the light that shines on the object. check your reading What color band or bands does a red apple absorb a white. Chapter 17 Electromagnetic Waves 577,Page 6 of 7,Primary Colors of Light. The human eye can detect only three color,bands red green and blue Your brain per. ceives these three colors and various mixtures,of them as all the colors These three colors of.
light which can be mixed to produce all possi,ble colors are called primary colors When all. three colors are mixed together equally they,appear white or colorless Whenever colored. light is added to a mixture specific wavelengths,are added Mixing colors by adding wavelengths. is called additive color mixing,An example of the practical use of primary. colors is a color television or computer monitor,The screen is divided into thousands of tiny.
bundles of red green and blue dots or pixels,A television broadcast or DVD sends signals that. tell the monitor which pixels to light up and, Primary colors of light when to do so By causing only some pixels to give off light the monitor. combine to make the, can mix the three colors to create an amazing variety of colorful images. secondary colors yellow,cyan light blue and, magenta dark pink check your reading What does an equal mix of all three primary colors produce. Mixing Colors,SKILL FOCUS,What is black ink made of Observing.
1 Trim each of the filter papers to a disk about 10 cm 4 in in diameter Make. two parallel cuts about 1 cm 5 in apart and 5 cm 2 in long from the edge. of each disk toward the center Fold the paper to make a flap at a right angle MATERIALS. 2 Use a different marker to make a dark spot in the middle of the flap on 3 coffee filters. each disk 3 brands of, 3 Fill each of the cups with water Set one of the disks on top of each cup so black felt tip. that the water covers the end of the flap but does not reach the ink spot. 4 After 15 minutes examine each of the flaps water. WHAT DO YOU THINK 30 minutes, What did you observe about the effects of water on. the ink spots,How do the three different samples compare. CHALLENGE Write a hypothesis to explain, what you observed about the colors in a black marker. 578 Unit 4 Waves Sound and Light,Page 7 of 7,Primary Pigments.
Remember that two factors affect an object s color One is the wave. lengths present in the light that shines on the object The other is the. wavelengths that the object s material reflects or absorbs Materials. can be mixed to produce colors just as light can Materials that are. used to produce colors are called pigments The primary pigments. are cyan yellow and magenta You,can mix primary pigments just as. you can mix primary colors to,produce all the colors. The primary pigment colors are,the same as the secondary colors of. light The secondary pigment colors,are red blue and green the same. as the primary colors of light,The effect of mixing pigments.
is different from the effect of mixing,light Remember that a colored. The inks used to make the, material absorbs all wavelengths circles on this page are. except those of the color it reflects primary pigments. They combine to make, Yellow paint absorbs all wavelengths the secondary pigments. except yellow Because pigments red blue and green,absorb wavelengths whenever you. mix pigments you are subtracting, wavelengths rather than adding them Mixing colors by subtracting.
wavelengths is called subtractive color mixing When all three primary. pigments are mixed together in equal amounts all wavelengths are. subtracted The result is black the absence of reflected light. check your reading How is mixing pigments different from mixing light. KEY CONCEPTS CRITICAL THINKING CHALLENGE, 1 What are some ways in 4 Apply Imagine that you are a 6 Synthesize If you focus a red. which materials affect how firefighter searching a smoke light a green light and a blue. light is transmitted filled apartment Would using light on the same part of a. 2 How does a polarizing filter a stronger light help you see black curtain what color will. reduce glare better Explain your answer the curtain appear to be Why. 3 In order for an object to 5 Predict Higher energy EM. appear white which wave waves penetrate farthest into a. lengths must the light contain dense medium What colors. and the object reflect are more likely to penetrate to. the bottom of a lake,Chapter 17 Electromagnetic Waves 579. You have read that EM waves can interact with a material medium in the same ways that mechanical waves do Three forms of interaction play an especially important role in how people see light One form is reflection Most things are visible because they reflect light The two other forms of interaction are transmission and absorption trans MIHSH uhn is the passage of an EM wave through a

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