Unit Study Guide: Waves and Heat Transfer

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1 Name Date Per Unit Study Guide: Waves and Heat Transfer I Can Statements I Can Statements are the learning targets for each unit. By the time you take the test for this unit, you should be able to confidently say: I can identify the different parts of a wave. I can explain the relationship between energy and wavelength. I can explain the relationship between energy and amplitude. I can explain the way light moves through different mediums. I can explain the way sound moves through different mediums. I can explain how heat transfers through convection, conduction and radiation. I can explain that white light is made of many different colors of light. Teach the Concepts One great way to study is to explain concepts to others. Teach the following concepts to a parent, grandparent, aunt, uncle, or even an older sibling. ü Explain how energy travels. ü Describe and give examples of the measurable parts of an energy wave. ü Explain the difference between wavelength and amplitude. ü Describe and give examples of all three types of heat energy transfer. ü Explain what part of the electromagnetic spectrum humans can see. ü Name the mediums through which light and sound can travel. ü Explain refraction, and give examples. Read/Summarize Signature Waves: Remember, a wave transfers energy through matter or space, and energy is needed to create a force (a push or a pull). Waves carry energy, and waves can go through many things like glass, walls, air, water, and even empty space. There are many kinds of waves, light waves, sound waves, water waves, etc.; but all waves have the same basic characteristics. Wave characteristics include: cycles, amplitude, frequency, and wavelength. Some examples of waves are sound waves, radio waves, microwaves, visible light waves, earthquake waves, cell phone waves, and water waves. Mediums: The substance a wave travels through is called a medium. If a wave moves through water then water is the medium for the wave. If a wave goes through air then air is the medium for that wave. Some waves have many mediums. Light, for example, can travel through air, water, glass, and even empty space (and other things as well).

2 Wave Speeds: Wave speed changes depending on the medium through which the wave is travelling. Sound waves travel faster in dense mediums. For example, although noises might sound strange to us underwater, the sound waves are travelling significantly faster in the water than they would be in the air. They would travel even faster through a steel rod, because it has a higher density. Light, on the other hand, travels fastest in empty space. Light waves slow down when they enter a medium with a higher density. If the light enters the dense medium on an angle, the change in speed will cause the light to change direction slightly, or bend. This is called refraction. Visible Light: Although most light appears to be white, white light is actually a blend of all seven colors of light (red, orange, yellow, green, blue, indigo, and violet). Each color has a slightly different wavelength. The combination of all the colors creates white light. White light can be separated into separate colors by refraction. This is why a prism can create a rainbow of colorful light. In nature, water droplets suspended in the sky following a rain storm act as millions of prisms, creating a rainbow. Wave Parts: Wavelength is a measure of the distance between two crests or two troughs of a wave. Amplitude measures the height a wave is going above or below the resting position of the wave. In a transverse wave, amplitude is the measure from the resting position to either the crest (high point of the wave) or to the trough (low point of the wave). Think of amplitude in terms of a wave on water. The bigger (taller) the wave the more the boat moves up and down because of greater amplitude. It takes energy to move a boat in the water. But you ll notice the boat stays in the same place, it only goes up and down. This is because the energy that made the wave is transferring energy through the water, but not transferring the water itself. The water is the medium that the energy is being transferred through. Energy Source: All waves begin with an energy source. For example, rocks breaking at the focus of an earthquake are the source of energy that creates seismic waves (earthquake waves). A light bulb is an energy source that produces visible light waves. Nuclear activity in the sun is the energy source that produces infrared, visible light, and ultraviolet waves. In all cases, waves move away from the source in all directions. As the waves spread away from the source, the energy becomes less intense. This is why a fire engine siren is deafeningly loud when you are standing 20 feet away from it, but doesn t sound very loud when it is half a mile away. Heat Transfer: Heat is in constant motion. It flows from warmer areas to colder areas until an overall equal temperature is established. The movement of heat from a warmer object to a cooler one is called heat transfer. There are three methods of heat transfer: conduction, convection, and radiation.

3 Conduction is the movement of heat energy through a substance or from one substance to another by direct contact of atoms and molecules. Heat moves directly from one molecules to another. Convection is the transfer of heat in a liquid or gas as groups of molecules move in currents from one region to another. Warm air is less dense than cooler air. The less dense air rises while the cooler more dense air sinks. The heavier, colder air sinks and pushes the lighter, warmer air up. This circular movement is called a convection current. Radiation is heat energy transmitted through empty space or heating the empty space by electromagnetic waves or infrared rays. This process involves only the molecules of the substance radiating the heat. Radiation can occur through a vacuum and is the way the sun s heat is transferred to Earth. Check Yourself All energy travels as. Draw an example of a wave and label its measurable parts. Give examples of 3 different types of heat energy transfer and explain how they work (draw if you like): Draw a model that represents energy starting at the sun and ending with accomplishing work: Explain what happens to white light that shines through a prism. Why doesn t a laser behave the same way?

4 On the table below, mark which mediums each wave type can travel through by circling Yes, No, or Sometimes. If the wave can travel through a particular medium, write an example! Solid Liquid Gas Vacuum (empty space) Light Sound EQ waves: P-waves EQ waves: S-waves Convection Conduction Radiation Farm Boy is standing 15 feet from a lit light bulb. Creepy Boy is standing 25 feet from the light bulb. Draw waves to show energy moving from the source. Who will hear the sound the loudest? Explain. Angry Purse Girl is standing 2 feet away from a blasting speaker. Big Hair Lady is standing 14 feet away from the speaker. Draw waves to show energy moving from the source. Who will hear the sound the loudest? Explain. What can you conclude about waves as they move farther away from the source?

5 On each of the pictures below, label any conduction, convection, and radiation that you see. Then explain. Explanation: Explanation: Explanation: Below is a copy of the electromagnetic spectrum. In each of the empty boxes draw what that wave type looks like. For example, if the wave has a high frequency, draw a wave with a short wavelength. In the table below, draw a wave (transverse) that matches the descriptions. High Amplitude Low Amplitude Long Wavelength Short Wavelength