Slide 1 / 131 Slide 2 / 131 4th Grade Waves, Light & Information 2015-11-17 www.njctl.org Slide 3 / 131 Slide 4 / 131 Table of Contents Click on the topic to go to that section What are Waves? · What are Waves? Describing Waves · Sound · Sight · Color · Mirrors · Refraction · Digitized Information · Return to Table of Contents Slide 5 / 131 Slide 6 / 131 Where have you seen waves? What are Waves? Each of these examples move up and down and across in a regular pattern (you never see just one wave at the beach). At the beach? On a guitar? At a baseball game? Can you think of any other times you see something moving like that?
Slide 6 (Answer) / 131 Slide 7 / 131 What are Waves? Water Waves We're now going to make some waves of our own. Each of these examples move up and down and across in a regular pattern (you never see just one wave at the beach). Teacher Notes Students might bring up a slinky, Your teacher holding on to a rope and wiggling it, should have a waves coming from a moving boat, basin filled etc. Some might also talk about with water. light or sound. [This object is a teacher notes pull tab] After dropping a rock or other object into the water basin you should have seen something like the image above. Can you think of any other times you see something moving like that? Slide 7 (Answer) / 131 Slide 8 / 131 Water Waves Water Waves We're now going to make some waves of our own. Here is a simulation of what we just saw. This is the water wave in a basin Can you see the waves moving out from the lower left corner? and a wave in a rope demo. Teacher Notes What started these waves moving? Fill a basin with water and drop a rock into it. You can see as the Your teacher waves move outward from that should have a point. basin filled with water. For the rope, hold it at one end and move the other end up and down. [This object is a teacher notes pull tab] After dropping a rock or other object into the water basin you should have seen something like the image above. Slide 8 (Answer) / 131 Slide 9 / 131 Water Waves Water Waves Here is a simulation of what we just saw. Before the rock is dropped, the water is flat, calm, and not moving . Can you see the waves moving out from the lower left corner? The scientific word for that is equilibrium. Teacher Notes What started these waves moving? Before we drop the rock, the water is in equilibrium. An object, like a rock, was dropped into the water in the lower left corner- you can see the splash [This object is a teacher notes pull tab]
Slide 10 / 131 Slide 11 / 131 Water Waves Rope Waves Here's a simulation (remember - it's a model that helps us The rock falls in the water, sinks, and pushes the water out of its understand how the real thing works) of the way. This water goes up and over the surface and moves away waves that were created in the rope lab. from the rock - this is a wave! What disturbance created these waves? The water is no longer in equilibrium, it is disturbed. The waves The light blue curvy line is a picture of the rope. move in a nice pattern, repeating themselves! Each little dot is just one point on the rope. Slide 11 (Answer) / 131 Slide 12 / 131 Rope Waves Rope Waves Here's a simulation (remember - it's a model that helps us Look at any dot on this simulation. understand how the real thing works) of the waves that were created in the rope lab. Teacher Notes Which way is that single dot moving? Right? Left? What disturbance created these waves? The rope was wiggled up and down. Up? Down? The wiggling is the disturbance - like the rock that was dropped in the water. [This object is a teacher notes pull tab] The light blue curvy line is a picture of the rope. Each little dot is just one point on the rope. Slide 12 (Answer) / 131 Slide 13 / 131 Rope Waves Transverse Wave The dot is moving up and down, as you can see in the simulation Look at any dot on this simulation. below. Teacher Notes Which way is that single dot moving? There is a special name for a wave where the individual dots The dots are moving up and down - Right? Left? move up and down. It's called a transverse wave. they are not moving left to right, Up? Down? even though the wave is moving left to right. This is a tricky concept and we'll be talking more about this later. [This object is a teacher notes pull tab] If this were a water wave, the dots would be little drops of water. If it were a rope wave, the dots would be the pieces of the rope moving up and down.
Slide 14 / 131 Slide 14 (Answer) / 131 1 Waves are regular patterns of motion that are caused by 1 Waves are regular patterns of motion that are caused by a disturbance. a disturbance. True True Answer False False TRUE [This object is a pull tab] Slide 15 / 131 Slide 15 (Answer) / 131 2 What kind of a disturbance will cause a water wave to 2 What kind of a disturbance will cause a water wave to start? start? A Listening to the water. A Listening to the water. Answer B B Dropping a rock into a basin of water. B Dropping a rock into a basin of water. C Looking at the water. C Looking at the water. [This object is a pull tab] Slide 16 / 131 Slide 16 (Answer) / 131 3 As you wiggle a rope, a transverse wave moves along 3 As you wiggle a rope, a transverse wave moves along the rope away from your hand. Which way does each the rope away from your hand. Which way does each piece of the rope move? piece of the rope move? A Up and down. A Up and down. Answer B Outward from your hand B Outward from your hand A C Inward towards your hand C Inward towards your hand [This object is a pull tab]
Slide 17 / 131 Slide 18 / 131 Describing Waves Describing Waves Scientists like to name things - this helps them understand what is happening in the world and helps them invent new things. There are a lot of different names for waves! Return to Table of Contents Slide 19 / 131 Slide 20 / 131 Describing Waves Equilibrium Let's begin by drawing a dotted line going through the center of a transverse wave (remember, this is a wave where the disturbance is going up and down as the wave moves left or right). The dotted line actually means something. If you were looking at a lake with no waves on it, would it look like that dotted line? What term did we learn which means when something is flat and calm? Slide 20 (Answer) / 131 Slide 21 / 131 Equilibrium Crest All transverse waves have a crest. Teacher Notes The dotted line shows the water or rope is in equilibrium (calm) - and The crest is the highest by moving up or down from the point the wave reaches. dotted line, the particles (water Think of a crest like the drops or pieces of the rope) are top of a hill. The dotted line actually means something. If you were looking moving away from equilibrium. at a lake with no waves on it, would it look like that dotted line? What term did we learn which means when something is flat [This object is a teacher notes pull tab] and calm? How many crests does this wave have?
Slide 21 (Answer) / 131 Slide 22 / 131 Crest Trough All transverse waves have a crest. All transverse waves also have a trough. Teacher Notes The crest is the highest 4 crests point the wave reaches. Think of a crest like the top of a hill. The trough is the lowest point the wave reaches. [This object is a teacher notes pull tab] How many troughs does this wave have? How many crests does this wave have? Slide 22 (Answer) / 131 Slide 23 / 131 Trough Describing Waves Can you see that the wave goes above the dotted line All transverse waves also have a trough. (equilibrium) just as much as it goes below the line? Teacher Notes 3 troughs The trough is the lowest point the wave reaches. [This object is a teacher notes pull tab] Using the terms that we just learned, can you see that the ________ and the _________ are equally far away from the How many troughs does this wave have? dotted line? Slide 24 / 131 Slide 24 (Answer) / 131 Amplitude Amplitude This distance from the dotted line (equilibrium) to the crest or the This distance from the dotted line (equilibrium) to the crest or the trough is called the amplitude of the wave. trough is called the amplitude of the wave. Teacher Notes The two distances are equal. The distance from the equilibrium line to the crest is the same as the distance from the equilibrium line to the trough. [This object is a teacher notes pull tab] What do you notice about these two distances? What do you notice about these two distances?
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