ࡱ > o bjbjT~T~ 7 6 6 g _ _ _ _ _ s s s s t < s w R # # # # # Fw Hw Hw Hw Hw Hw Hw $ { } V lw _ lw _ _ # # w _ # _ # Fw Fw m Zv # rF s p N 2w w 0 w p ^ ~ t ~ Zv ~ _ Zv lw lw w ~ % : Subject: Science Unit: Light and Sound Grade: 4 PLOsProcesses and Skills of Science Make predictions, supported by reasons and relevant to the content Use data from investigations to recognize patterns and relationships and reach conclusions Physical Science: Sound and Light Identify sources of light and sound Explain properties of light (e.g., travels in a straight path, can be reflected) Explain properties of sound (e.g., travels in waves, travels in all directions) Lesson # and TitleActivitiesMaterialsAssignment/ AssessmentSources of SoundWe all hear sounds but where do they come from? Things that produce sounds are called sound sources. Most sound sources are objects moving back and forth very quickly or vibrating. The vibrations that produce sound are far too fast to see but you can often feel them. Sound from vibrations: Thread one end of a string through the hole in a ruler and tie it securely. Go outside and hold the string near the free end. Now whirl the ruler around your head. You should hear a strange sound. What happens to the sound if you whirl the ruler faster? Whats happening? As it spins, it makes the air vibrate, producing the strange sound. The faster the ruler turns, the more high-pitched the sound becomes. Sound from a shock wave: Follow scanned instruction to make the banger. Grasp your noisemaker between two fingers and a thumb. Hold it above your head and bring is down fast, as if you were hammering a nail When you stop, the paper fold flies out, causing a loud bang. Whats happening? When the folded center of the noisemaker flies out, it pushes air in front of it, creating a shock wave. The shock wave is heard as a loud bang. String Rulers with a hole at one end Piece of paper for each student Overhead of scanned instructionsSources of LightLight is all around us but where does it come from. Things the produce light, such as the sun or a flashlight are called light sources. The sun and the flashlight bulb glow because they are hot. This is called incandescence. Hot objects give off red light. If they get even hotter, they give off yellow light. Really hot things glow white. Some light sources, such as fireflies and television screens are not hot. They give off light by luminescence. White hot experiment: Look at a bulb using the magnifying glass. Can you see the filament? The filament is the metal wire in the bulb that glows to give off light Connect the bulb to the 1.5V battery, using wires as shown. Now connect the bulb to the 4.5V battery. What is different this time? What is happening? The filament heats up as electricity flows through it, producing light by incandescence With the 1.5V battery, the filament gives off yellow light. With the 4.5V battery, the filament gets much hotter and gives of bright white light Sweet Light: Put a few sugar cubes into a plastic bag and take groups of students into a very dark room (possibly the bathroom). Wait at least 5 minutes to let everyones eyes adjust to the dark. Then use the rolling pin to crush the sugar cubes. Can you see the tiny flashes of light. Whats happening? There are many kinds of luminescence. One kind is triboluminescence, in which some materials produce light when they break. Sugar cutes are triboluminescent When the sugar is crushed, the atoms break apart and give off blue light1.5V battery 4.5V battery 1.5V light bulb Magnifying glass Insulated wire with the ends strippedAssessment: Try this at home. Make the room dark and turn off the television. Hold a flashlight against the television screen. Turn on the flashlight for about a minute, then turn it off. When you move the flashlight away from the screen, what do you see? How can you explain what is happening? Write up a short explanation.Sound TravelsGo over homework assignment. Ask students for their explanation of the glowing television. Whats happening? A television screen is a light source. The inside of the screen is coated with dyes that can glow by luminescence. When you shine the flashlight, the dyes in the screen store its light energy. They give off the energy gradually, producing a faint glow over a few minutes The vibrations that cause sound travel in all directions as waves. If you shouted to someone standing 1,116 feet (340metres) away from you the sound of your voice would take about one second to reach the other person. Most of the sound we hear travels through the air, but sound can also travel through solids and liquids. How a megaphone makes your voice louder: Pour a shallow layer of water into a shallow pan. Wait for it to settle. Touch the waters surface with your finger. Quickly move your finger up and down to make water waves that travel in every direction, just like sound waves through the air. Put two pencils in the water pointing away from your finger in an open-triangle shape. Make the waves again where the pencils are close together. What happens to the waves now? Whats happening? The more spread out a sound wave is, the quieter the sound. The pencils in the water do not allow the water waves to spread out much. In the same way, the sides of a megaphone keep sound waves from spreading out of quickly, so your voice sounds louder. String sounds: Tie about 40cm of thread to a spoon, near the middle. Wrap the free end of the thread around a finger and swing the spoon so that it hits against the table. Listen to the sound this makes then do it again, but this time put the finger with the thread wrapped around it in your ear. Is the sound louder or quieter when you put your finger in your ear? Whats happening? Sound travels through solids faster and often more clearly than through the air. Hitting the table makes the spoon vibrate and it produces a sound. The sound waves spread out in air, so it sounds quiet. But sound waves in the thread do not spread out as they travel so they sound is louder Did you know? In outer space there is no air, so there is nothing to carry sound waves. Space is absolutely silent. Water A shallow pan Two pencils Thread A large spoon Light TravelsWhen you turn on a flashlight, the bulb seems to light up immediately. Actually, it takes a short time for the light to travel to your eyes; less than a hundred-millionth of a second! Light travels at 186,282 miles per sec (299,792km/sec). But even though it travels at such an incredible speed light from the sun takes eight minutes to reach us on earth. Seeing the light: Light does not spread out like sound does. It travels in straight lines, but you can only see the beams when the light shines into your eyes. Turn the lights off and have a classmate shine the flashlight from one side of the room to the other, so that the beam passes in front of the other students eyes. They can not see the beam. Sprinkle talcum powder in the path of the light bean. Suddenly, you can see where the light is going. Have the student holding the flashlight block part of the beam with their finger Whats happening? When the light from the flashlight hits the tiny particles of talcum powder, it bounces off in all directions. Some of the light bounces into your eyes, so you can see the path of the beam. When the air is clear, there is nothing to bounce the light into your eyes so the beam goes past you without you seeing it. Passing through: Have a classmate shine a flashlight in your direction, but not directly into your eyes. What happens when they hold different materials in front of the flashlight? Try clear plastic, tracing paper, wood, metal and a hand. Does light pass through some materials better than others? Whats happening? You can clearly see through some materials they are called transparent. Translucent materials, like tracing paper, let some light through but you cant see through them clearly. Opaque objects let no light through at all When light hits an opaque objects, a shadow forms. A flashlight(s) Talcum powder Objects make of different materials (clear plastic, tracing paper, wood, metal, etc)Different Tones of SoundThe sound of your voice is produced by small flaps of skin, called vocal cords, inside your throat. When you sing or speak in a high voice, your vocal cords vibrate very quickly. When you make a low-pitched sound, they vibrate more slowly. All sounds may be high or low-pitched, depending on how rapid the vibrations are that cause them. High and low: Pour some water into a plastic pop bottle until it is half full. Blow across the top of the bottle to make a sound. Put more water into the bottle, and then blow across the top of the bottle again. How has the sound changed? Whats happening? The column of air inside the bottle vibrates when you blow across the top of the bottle. The shorter the air column, the faster the air vibrates and the higher the sound. Vibrating ruler: Place a ruler on a table so that some of the ruler hangs out over the edge. Press down hard on the ruler right at the edge, then twang the ruler so that it makes a sound. Can you see it vibrating? How can you make the sound higher or lower in pitch? Whats happening? The longer you make the vibrating part of the ruler, the slower it vibrates and the lower the pitch of the sound. Plastic pop bottle Water Plastic rulerMusical SoundsMusic is the sound that has a pleasing mixture of different vibrations. Different musical notes are produced by vibrations of different frequencies. Musical instruments are divided into three types, depending on how the sound is produced. Percussion instruments, such as drums and cymbals, produce sound when they are hit. Wind instruments, such as trombones or clarinets, produce sound when the air inside them vibrates. String instruments, such as violins and guitars, have strings that produce sound when they are bowed or plucked. Rubber band guitar: Remove the lid from the shoebox and cut a hole in the top. Glue one piece of wood to each end of the shoebox, on either side of the hole you have cut out. Leave to dry. Stretch the rubber bands across the top of the shoebox and the pieces of wood. Leave a gap of about 1cm between each rubber band. Pluck them with your finger. Now hold the bands with another finger and pluck again. What happens if you move that finger along the strings while you pluck them? Can you make different notes on your rubber-band guitar? Whats happening? When you pluck the rubber bands they vibrate and make a sound. The box vibrates too which makes the sound louder. There are three ways to raise the pitch of the note: stretching the band tauter, shortening the part of the band that vibrates (by holding it with your finger), or using a thinner band. Panpipes: Cut straws into eight different lengths. Lay the straws next to each other, from longest to shortest so that they are level along one end. Tape the straws together. Hold the level end of the panpipes against your bottom lip and gently blow across each pipe. Which pipes produce the highest notes? Which pipes produce the lowest ones? Can you play a tune on your panpipes? Whats happening? When you blow across the pipes the air inside them vibrates. The longer pipes produce lower notes, because long columns of air vibrate more slowly. The shorter lengths produce higher notes. Empty shoeboxes Large rubber bands Scissors Glue Pieces of wood about 1cm thick and as wide as the shoebox Plastic drinking straws TapeWhite LightMost light sources, including the sun and flashlights give off white light. It is called white light because it seems to have no colour. In fact, white light has more colour than any other kind of light. It is a mixture of red, orange, yellow, green, blue, indigo, and violet light. In some situations, all the colours separate to produce a continuous band of colour called the white light spectrum. For example, a rainbow forms when raindrops separate sunlight into a spectrum. Compact spectrum: Make a hole about 0.5cm in diameter in the middle of a piece of aluminium foil. Wrap the foil over the front of the flashlight, with the hole in the center. Place the compact disc on a table with the writing facing down. Turn on the flashlight and hold it so that light reflects off of the compact disc and into your eyes. You will need to have the compact disc between you and the flashlight and point the flashlight diagonally. Whats happening? The surface of a compact disc is covered with very small dents called pits. When light hits the pits, each colour reflects at a slightly different angle, producing the spectrum. A compact disk Flashlight Aluminium foilColoured LightThe bulbs in a cars brake lights produce white light but you see a red glow because the light shines through a red plastic filter. Filters remove certain colours from white light, while allowing the rest of the spectrum through. Some light sources produce only certain colours of the spectrum Have you ever wondered why the sun appears orange at sunset? As white light from the sun passes through the air, the blue and green parts of the spectrum are scattered in all directions. Only the red, orange, and yellow light gets through. Make a sunset: Shine a flashlight straight through the bowl of water toward you. What colour is the light? Add about half a teaspoon of milk to the water and stir thoroughly. Shine the flashlight through the water again. What colour is the light now? How does the light change when the milk is added? Whats happening? Tiny particles of fat in the milk scatter blue and green light more than they scatter other colours. You see the red, orange and yellow light more clearly just as you do at sunset. Lose the blues: Make a spectrum using a compact disc (from last class). Hold a clear, yellow, plastic folder between the flashlight and the disc. This makes the light yellow. What happens to the spectrum? Whats happening? When you shine white light through a yellow filter, orange, red, yellow and green light pass through it. These are the colours of the spectrum that will appear on the compact disc. The flashlight light looks yellow because the folder absorbs the blue, indigo and violet light. Class bowl filled with water Flashlight Milk Spoon A clear, yellow, plastic folder Aluminium foil Compact discHearing SoundWhen sound waves enter your ear, they make a tiny membrane of skin called the eardrum vibrate. These vibrations pass deep into the ear and are picked up by nerves which send messages to the brain. Sounds that are very loud or nearby make the eardrum vibrate more than those that are quiet or far away. Very loud noises can permanently damage your ears. Eardrum: Cut a balloon and open it out into a sheet large enough to fit over the top of the cup. Stretch the balloon over the top of the cup and hold it in place with a rubber band so that it stays tight. Sprinkle a few granules of sugar onto the balloon. Now shout or make other loud noises near it. What happens to the sugar? Whats happening? The sound waves hitting the balloon make it vibrate just like your eardrum. You can see the vibration when the sugar granules dance up and down. Go over diagram of the inner ear Sock it to me: Play some fairly loud music and hold two plastic cups over your ears How does the music sound? Then squash one sock into each cup and hold them over your ears again. How does it sound now? Whats happening? The music sounds quieter because the plastic cups and the socks absorb some of the sound waves so fewer of them reach your ears. Very loud sounds can damage your ears.Balloons Sugar Glass or plastic cups Rubber bands Two plastic cups Two clean socks A radio Diagram of inner earSeeing LightLight enters your eyes through the pupil (the black dot in the middle of your eye), then through the lens. The lens focuses the light at the back of the eye where a picture or image is formed. The back of the eye is connected to the brain by the optic nerve. Your eyes hold an image of what you see for about one fourth of a second after the light has entered them. Go over diagram of the eye Model of the eye: Fill a balloon with water until it is 10cm wide. Tie the balloon to keep the water in. Cut a piece of cardboard to cover the front of a flashlight. Cut an arrow shape out of the cardboard, and tape it to the front of the flashlight. Hold a magnifying glass right in front of the balloon. Point the flashlight at the balloon and turn it on. What do you see? Whats happening? You should see an image of the arrow at the back of the balloon. The image is upside down or inverted because the magnifying glass makes the light rays cross over each other as they pass through the balloon. Images in the eye are inverted too but the brain interprets them so we see them right side up.Diagram of the eye Balloon Piece of cardboard Scissors Flashlight Magnifying glass TapeReflecting SoundWhen sound hits a solid object it bounces off or reflects like a ball thrown against a wall. The reflected sound is called an echo. Echoes can be very useful. For example, sound traveling under ground reflects off of layers of rock. Recording these seismic waves can tell us much about the structure of those rocks. This is called seismic surveying. What angle? Open a book slightly and stand it about 30cm from the edge of a table. Lay one tube on the table with one end near the spine of the book. Hold a watch near the other end of the tube. Some of the sound made by the watch will travel down the tube and reflect off of the book. Hold the other tube to your ear and move it until you can hear the reflected sound of the ticking watch. Where do you have to move the tube? Whats happening? The sound of the watch travels down the tub and reflects off of the book. You can hear the echo when your ear is in the path of the reflected sound. Bouncing waves: Go outside, close your eyes and loudly say hello. Then hold a book about 20cm in front of your face with the cover facing you and again say hello. Can you hear the different? What happens if you use a sweater instead of the book Whats happening? There are small pockets of air in the wool of the sweater. These pockets trap and absorb sound so there is no echo. The book has no air pockets so it reflects the soundA watch that ticks Two cardboard tubes A hardback bookReflecting LightThe moon produces no light of its own but it still looks bright in the sky. What we see as moonlight is actually sunlight that has reflected off of the moon. Light reflects off of most things but it reflects much better off of white and silvery objects than dark ones. Some objects reflect only certain colours of light. A yellow pencil for example reflects only yellow light which is why it looks yellow. Moon shapes (To see why the shape of the moon changes from night to night): Tape one end of a string to a tennis ball. Stand in the middle of a dark room and hold the string so that the ball is just above your head and in front of you, suspended in the darkness, like the moon in space. Ask a classmate to shine a flashlight at the ball. Now slowly turn around, keeping your arm out. What do you see? What does the tennis all look like as you turn around? Whats happening? In this experiment, the ball in the moon, the flashlight is the sun and you are the earth The sun always shines on half the moon and the moon travels around the earth once every month. When the moon is between the earth and the sun, we cannot see any reflected light. We call this a new moon. When the earth is between the sun and the moon, we can see the whole face of the moon. This is a full moon. Black and white: Place two sheets of paper, one black and one white, next to each other on a table by a wall. Make the room dark and shine the flashlight on the white paper. You should see a patch of light on the wall. Now shine the flashlight on the black paper. What do you see? Whats happening? The white paper reflects much more light than the black paper does. This is how supermarket checkout scanners work a laser reflects off the black ad white lines of a barcode and a sensor detects the reflected light. Reflecting colours: Hold coloured sweater next to a wall in a dark room. Shine the flashlight on the sweater so that light reflects off the sweater. You should see a patch of coloured light on the wall Whats happening? White light from the flashlight is a mixture of many colours. The red sweater only reflects the red light from this mixture.Flashlight Tennis ball About 15cm of string Tape A sheet each of black and white paper A coloured sweaterMirrorsAny shiny surface can act as a mirror but some reflect better than others. The mirrors we use are coated with a shiny metal to reflect all of the light that falls on them. The picture or image in a flat mirror is reversed. Curved mirrors can make reversed images too. They can also make things look bigger, smaller or even upside down. Seeing it both ways: In a dark room, sit or stand facing a classmate about 1m apart. Hold a flat sheet of clear plastic vertically halfway between you. Shine a flashlight at your face. You should see a reflection of yourself in the plastic. What does your friend see? Ask your classmate to shine the flashlight on his or her face. Now you should see your friends face because the light has bounced off of it and passed through the plastic but what does your friend see? Whats happening? Most of the light that hits a clear plastic or glass surface passes through it this is why you can see your friend in step 3. But some light reflects off of the plastic surface. When there is no light passing through from the other side you can see the reflected light. This is why you see yourself in step 2. Magic window: Face a window and hold a piece of white paper up in front of your face. Now hold the magnifying mirror about 15cm from the paper so that it faces away from you and light from the window reflects onto the paper. You should see an image of the window on the paper If you dont see it, move the mirror closer to or farther from the paper until you do. Can you see an image of the window? Whats happening? Flat mirrors reflect light straight back where it came from but concave mirrors focus the reflected light. When the focused light hits the paper, you see an image. Reflect on this: Hold the magnifying mirror close to your face. Your image will be large and right side up. Now ask a classmate to hold the mirror at arms length (1-2m) from your face. What does your image look like? Whats happening? A makeup mirror is concave. Its bowl-shaped surface reflects light at an angle. When you are near the mirror, this angle creates an enlarged image. But when you stand farther back, the light rays crisscross before they reach your eyes so the image is upside-down.Flat sheet of clear plastic from a picture frame Flashlight A magnifying makeup or shaving mirror A piece of white paperBending LightAt the swimming pool, you might have noticed that people swimming under water look different from how they look out of the water. This is because light that has reflected off of their bodies ends as it leaves the water. This bending of light, called refraction, happens whenever light passes from one transparent substance to another Watch it bend: Cut a piece of cardboard that will cover the front of a flashlight. Make a slit in the middle of the cardboard about 0.5cm wide. Tape the cardboard over the flashlight. Add a few drops of milk to a glass bowl filled with water. Make the room dark and shine the flashlight into the bowl at an angle. Change the angle and watch the path of the light inside the milky water. Why does the beam of light bend as it enters the bowl? Whats happening? The light beam bends because it is passing through two different substances. The particles that make up the milky water are more closely packed than the particles of air so the light slows down. The change in speed changes the lights direction. Water colours: Fill a shallow pan with water and stand a mirror against one end o the pan, titled towards you. Hold a piece of white paper vertically in front of the pan. Shine a flashlight into the mirror so the light reflecting off of it hits the paper. What do you see? Whats happening? Light is a mixture of many colours. Each colour of light refracts at a slightly different angle so the colours spread out to form the bright spectrum you see reflected on the paper.Flashlight Cardboard Tape Scissors A glass bowl filled with water Milk Flat mirror Shallow pan White paperLensesHave you ever wondered how the lenses in your camera or glasses work? Lenses are specially shaped pieces of transparent material (usually glass) that can make things look different because light refracts as it passes through the lens. Slide projector: In a dark room, turn on a lamp and hold a piece of paper with a shape cut out of it over it. Now hold a magnifying glass about 10cm in front of the paper. Can you see an image of the cut-out shape on the ceiling or the wall? What happens if you move the magnifying glass? Whats happening? Light passes through the paper then refracts as it passes through the magnifying glass. When the refracted light shines onto a surface you can see the image of the shape. But it will only form if the magnifying glass if just the right distance from the paper. What magnification: Draw a line 3cm long on the paper. Look at the line through a magnifying glass and try to draw how long the line looks. Measure the line you have drawn. Whats happening: Magnification tells you how much bigger a lens makes things look. For example if your line measures 6cm long, your magnifying glass has a magnification of 2x Water lens: Place a drop of water on a picture in a magazine with glossy pages. Look at the picture through the drop. What do you see? Whats happening? A drop of water is a simple lens. It can make things look bigger or smaller. Light from an object passes through the water and refracts, making an image of the object. The type of image depends upon whether the object is far from or close to the lens.Magnifying glass Desk lamp Piece of paper with a shape cut out of it Paper Ruler A magazine with glossy pages S X * + k l m n q ɽ~p~~i\U hFe h7 h*$ h7 PJ nH tH h# h7 h7 CJ OJ QJ ^J aJ h7 5CJ aJ h7 h7 \]^J nH tH h7 h7 ^J h7 ^J h7 h7 \]^J h# h7 CJ aJ h# h7 5CJ aJ h5F h7 CJ aJ h7 CJ aJ h