2024_01_01-CONS127-A4

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University of British Columbia *

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127

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Astronomy

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Apr 3, 2024

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pdf

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1 Cons 127 Observing the Earth from Space Assignment 4: What Can I See? The Electromagnetic Spectrum, Wavelengths and Spectral Resolution Instructor: Chris Colton Office: FSC 2223 chris.colton@ubc.ca TA: Evan Muise (evan.muise@ubc.ca) For this assignment you will… • Learn how to characterize the electromagnetic (EM) spectrum • Understand the relationship between wavelength, frequency and energy • Learn how the EM spectrum is used in remote sensing • Be introduced to the spectral properties of different materials • Understand the use of EM channels in remote sensing platforms Submit your answers in accordance with the posted Lab Quiz (in CANVAS): • Assignment due date: Thursday, March 7 th , 2024 at 11:59 pm Pacific Standard Time • Answers to questions 1 through 20. The total points of the lab are 50. • Any screenshots or supplemental attachments (if needed)
2 Part 1: The EM Spectrum As you learned in lecture, remote sensing uses different wavelengths of the electromagnetic (EM) spectrum to observe the Earth. The EM spectrum is the range of different values that the wavelength/frequency of light can take – with the longest wavelengths and lowest frequencies represented by radio waves (10 6 μm, up to hundreds of meters in length), and the shortest wavelengths and highest frequencies represented by gamma rays (10 -6 μm, smaller than the diameter of an atom). Visit https://applets.kcvs.ca/ElectromagneticSpectrum/electromagneticS pectrum.html . This is a website that allows you to explore the EM spectrum. Use the sliding bar to examine difference regions of the visible light spectrum, which goes from 380nm to 780nm. Note how the frequency (Wave View) and energy (Photon View) change as wavelength increases or decreases. The wavelength of your cursor can be found in the white box. Explore this tool, then answer the following questions. Figure 1 Example of the visible light spectrum from the KCVS website As you can see, the difference in size of the longest and shortest EM wavelengths is 12 orders of magnitude! To put this in perspective, the distance from the Earth to the Sun is about 149,600,000,000 m (or 1.496 x 10 11 m), an order of magnitude less; so, if you visualize a micrometre as a metre, the EM spectrum is really long! Check out Episode 5 of Cosmos: A Spacetime Odyssey (It’s on Netflix, and sometimes you can find episodes on YouTube), to get immersed into the EM spectrum even further.
3 Q1. What happens as you move the cursor from violet light to red light (left to right)? (1.5 points) a) Wavelengths get shorter b) Wavelengths get longer c) No change Q2. Look under Wave View as you adjust the cursor. What happens to frequency as wavelengths get shorter? (1.5 points) a) Frequency increases b) Frequency decreases c) No change Q3. As you move the slider around the visible spectrum, what is the relationship between frequency and energy? (1.5 points) a) Energy increases as frequency increases b) Energy decreases as frequency increases c) Energy increases as frequency decreases d) There is no relationship and the numbers are random Q4. Set the visible spectrum to 450nm. What color is shown? (1.5 points) a) Red b) Blue c) Green d) Orange Look at the entire electromagnetic spectrum (EM) above the visible light spectrum bar. Note that γ means “gamma”. Q5. Which type of radiation has the longest wavelength? (1.5 points) a) Gamma b) Infrared c) Microwave d) Radio Q6. Which type of radiation has the shortest wavelength? (1.5 points) a) Gamma b) UV c) X-rays d) Radio
4 Except for the case of active remote sensing technologies (and thermal and night light sensors), the energy sensed by satellites and airplanes observing the Earth entirely originates from the Sun. The wavelengths that pass easily through the Earth’s atmosphere are called atmospheric windows. One obvious atmospheric window is the visible light range, which is also the range of peak output by the Sun. Explore this webpage on light and telescopes for more information on how we use the EM spectrum https://www.sciencelearn.org.nz/resources/1625-light-and-telescopes . Then answer the following questions. Q7) Which part of the EM spectrum do optical telescopes use? (1.5 points) a) Radio waves b) Micro waves c) Visible light d) Ultraviolet waves Q8) Which type of radiation is best for astronomers to use when detecting background radiation from the origin of the universe? (1.5 points) a. Microwave b. Gamma rays c. Infrared d. Radio e. X-rays Q9) According to the article, what are false colors? (1.5 points) a. Parts of the EM spectrum we haven’t discovered yet b. Parts of the EM spectrum which can’t be seen with the naked eye, but which computers can turn into visible spectrum colors c. Colors based on non-EM spectrum information such as elevation Q10) According to the video “Detecting light in space”, why do the X-ray telescopes need to be put in space, but radio telescopes can be used on Earth? (The i button can be clicked to view a transcript). (1.5 points) a. X-rays don’t penetrate the atmosphere, but radio waves do b. Radio waves don’t penetrate the atmosphere, but X-rays do c. X-rays are used to detect objects in space such as galaxy clusters, whereas radio waves are used only for objects on Earth d. Both X-ray telescopes and radio telescopes work best in space, but either can be used on Earth
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