A115 Exploration 4: Temperature In this week’s online segment, we’ll explore infrared light, and what it tells us about the universe. During class, we’ll u
A115 Exploration 4: Temperature In this week’s online segment, we’ll explore infrared light, and what it tells us about the universe. During class, we’ll use an infrared camera to demonstrate how the objects around us glow at wavelengths our eyes cannot see. Objects radiate light depending on their temperatures. Cool objects glow in radio or infrared light, while warmer objects like stars glow in optical light. The hottest objects in the universe glow in ultraviolet, x-ray, and gamma-ray light.
This exploration should take about an hour to complete, the equivalent of one class period. And if you want to play with the infrared camera yourself, please attend one of the scheduled help sessions this week. Be sure to watch the video that is part of this week’s reading assignment.
Learning Goals:
Students should be able to
Describe how an object’s thermal emission spectrum depends on temperature.
Explain how temperature can be measured using the color of an astronomical source.
Explain now astronomers can determine the temperature of astronomical objects using Wien’s Law.
What to Hand In:
This Exploration should be submitted online using the Word form below. Be sure to answer all questions.
Ex04_Temperature_Form.docx
Come to one of the Free Help Sessions if you need help with this Exploration. The schedule for help sessions is available in the Syllabus. A115 – Birth & Death of the Universe
Exploration 4: Temperature
NAME: Click here to enter name.
Due by 11:59 PM on Friday, Feb. 8. Late assignments one point.
Enter your answers on this form and submit it via the Canvas assignment tool
Learning Goals: Students should be able to:
•
•
•
Describe how an object’s thermal emission spectrum depends on temperature.
Explain how temperature can be measured using the color of an astronomical source.
Explain now astronomers can determine the temperature of astronomical objects using
Wien’s Law.
What to Submit:
• Submit this worksheet online using the Canvas assignment. Be sure to answer all
questions in Parts 1, 2, and 3.
Getting Started: Review section 5.1 in the text and watch the video in Unit 2 about infrared
light.
Part 1 – Thermal Spectra
1.1 How does the total energy emitted (the area under the curve) change with temperature?
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1.2 How does the wavelength at which the most light is emitted change with temperature?
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Part 2 – The Star Cluster Messier 47
2.1 Examine the dozen or so brightest stars in the cluster. What range of color do you see?
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2.2 Compare the colors of Star A and Star B. Based on their color, which star is hotter, and
why?
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Part 3: Estimating Temperature from Peak Wavelengths
The Sun is the brightest in green light, about 500 nanometers. Use Wien’s Law to estimate the
temperature of the Sun’s outer layers. Describe how you calculate the temperature.
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3.1 A microwave telescope “sees” microwave light coming from all directions in the sky. This
microwave signal is fairly strong, accounting for about 1% of the “noise” detected by a
television antenna set “off channel.” The microwave emission is brightest at a wavelength of
1 x 106 nanometers. From Wien’s law, estimate the temperature of the source of the
microwave emission.
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