Let's Investigate
The electromagnetic spectrum includes many different wavelengths of radiation; some are in the visible part of the spectrum while others are not. In this lab you will be focusing on the UV, visible, and infrared parts of the spectrum.
All objects emit electromagnetic radiation. The electromagnetic spectrum an object produces is dependent on its temperature. This is seen in studies on blackbodies. An ideal blackbody is one which absorbs and then re-emits all radiation that it receives. While only blackbodies re-emit all the light they absorb, all objects will re-emit some light, the wavelength of which is dependent on their temperature. In this investigation you will study the relationship between the temperature of an object and the electromagnetic spectrum that it emits.
Before you begin, click the Word or PDF link below to download your assignment worksheet. Then, read through the tabs below for the instructions. When you have completed the lab and the assignment, submit your worksheet to your teacher.
| Word |
Attribution: PhET Interactive Simulations | University of Colorado | https://phet.colorado.edu
The investigation consists of the parts shown below. Click the button below to download the instructions OR click through each tab to read and follow the steps to complete the investigation.
Exploring the
Simulation
Blackbody Spectrum, Temperature, and Color
When you open the simulation, there are many different sections shown on the screen.
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On the left is a graph showing spectral power density vs. wavelength. The wavelength is in µm. This graph shows the spectrum given off by objects of different temperatures. The spectral power density is the rate of energy emitted per area for each wavelength within the spectrum of the object. At the top of the y-axis and at the end of the x-axis are magnifying glasses with – and + signs. Click on these and answer Questions 1 and 2 on your assignment worksheet.
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Above the graph are three letters, B, G, and R. These letters stand for the colors blue, green and red. The circles above them are filled in with the color when that color is present in the spectrum of the object being studied. Next to these letters is a star which shows the color that the combination of these colors produces. Observe these for the default values and answer Question 3 on your assignment worksheet.
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To the right of the graph is a section to select different values that will be shown on the screen. Select “Graph Values” and then look at what was added to the graph. Answer Question 4 on your assignment worksheet.
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Select “Labels” and then answer Question 5 on your assignment worksheet.
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On the right of the screen is a thermometer with the temperatures of different objects marked. The default value is the sun, but this can be changed by dragging the marker on the right up and down. The temperature is shown at the top of the thermometer. Answer Question 6 on your assignment worksheet.
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Lower the temperature to that of Earth. You may need to use the magnifying glasses with – and + signs to see all parts of the curve. Fill in the row for Earth on the data table on Question 7 on your assignment worksheet.
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Raise the temperature to 3000 K, which is the temperature for a lightbulb. Fill in the row for lightbulb on the table on Question 9 on your assignment worksheet.
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Raise the temperature back up to that of the sun and fill in the information on the data table in Question 7 of your assignment worksheet.
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Raise the temperature up to that of Sirius A and record the information on the data table in Question 7 of your assignment worksheet.
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Based on the information from the data table in Question 7 on your assignment worksheet, answer Questions 8– 13 on your assignment worksheet.
