Colorado Physical Science Knowledge Check

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timer Asked: Jan 30th, 2019
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Question Description

The knowledge check and science in action are attached below.

Link for sciece in action: http://phet.colorado.edu/sims/blackbody-spectrum/blackbody-spectrum_en.html

1. Introduction Choose One • 10 points It is mentioned in the week 4 course notes that the understanding of something called blackbody radiation lead to the formulation of quantum mechanics. This first part of your Physical Science in Action this week will take a brief look at this phenomenon. As a reminder, here is a picture of the electromagnetic spectrum. It is oriented in the same direction as the spectrum you will use in today's simulation. Have you ever noticed that on a cool winter day that your house feels much cooler than on a warm summer day even though your thermostat is set to the same temperature? You are probably also aware that as objects heat up they will begin to give off visible light and also change color as they get hotter. For example a piece of metal placed in a furnace will begin to glow deep red, then orange, and then become “white hot”. Why do you think this is? Both of these questions will be easily answered by learning about blackbody radiation. Open the following link: http://phet.colorado.edu/sims/blackbody-spectrum/blackbody-spectrum_en.html It just so happens that regardless of the material, when objects are heated up they will start to glow and change colors at near identical temperatures. The plot that you see is called a blackbody spectrum. This plot tells us the intensity or the “amount” of light that an object will emit at different wavelengths (or “colors”). The visible wavelengths are marked by their colors on the plot. To the right of the visible band is lower energy infrared light. To the left of this band is higher energy ultraviolet (UV) light. Click the + button that is to the left of the intensity scale (far left side of the screen) such that the top of the scale is at .001. (in the picture above the top of the scale says 100). Now use the temperature slider to the right, and take the temperature all the way down to 300 Kelvin (80 Fahrenheit). Now slowly begin to raise the temperature. At approximately what temperature would a heated material (metal, wood, etc.) begin to give off visible light at a deep red color? Note: This will be the temperature where your spectrum first begins to come off of the wavelength axis in the visible region, and so is giving off a small amount of red light. • • • • 2 500 K (440 Fahrenheit) 1050 K (1430 Fahrenheit) 1800 K (2780 Fahrenheit) 2500 K (4040 Fahrenheit) 2. Blackbody Spectrum Choose One • 10 points Click the - button that is to the left of the intensity scale to zoom out such that the top of the scale is at 10. Move the temperature slider to that of a light bulb. The red part of the thermometer on the far right should just be touching the line marked light bulb. At approximately what temperature does the filament in a household light bulb operate? Note: This is written in blue in the simulation. • • • • 660 K (728 F) 1800 K (2780 F) 3000 K (4940 F) 5700 K (9800 F) 3. Blackbody Spectrum Choose One • 10 points What type of light does this light bulb produce most (i.e. at what wavelength does the spectrum have maximum intensity)? • • • • Infrared light Red visible light Violet visible light Ultraviolet light 4. Blackbody Spectrum Choose One • 10 points Click the - button that is to the left of the intensity scale to zoom out such that the top of the scale is at 100. Move the temperature slider to that of the Sun. The red part of the thermometer on the far right should just be touching the line marked Sun. Approximately what temperature is the surface of the Sun? • • • • 2100 K (3320 F) 4500 K (7640 F) 5700 K (9800 F) 9800 K (17,180 F) 5. Blackbody Spectrum Choose One • 10 points Based on the simulation, what type of light does the Sun produce the most? • 3 Infrared light • • • Green visible light Orange visible light Ultraviolet light 6. Blackbody Spectrum Choose One • 10 points Relative to the peak intensity in the Sun’s spectrum, the Sun emits nearly equal amounts of light across the entire visible part of the EM-spectrum. This is demonstrated by the star shaped symbol at the top of the simulation being white. Therefore, if you look at the Sun when it is directly overhead on a clear day, it will appear white. Click the - button that is to the left of the intensity scale to zoom out such that the top of the scale is at 316. Use the star shaped symbol above your graph and to the right of the blue, green, and red dots to estimate the temperature at which something will begin to glow blue. At approximately what temperature does the object gain a faint blue tint? Note: This will also be the temperature where the max intensity of the objects spectrum is in the blue portion of the visible spectrum. • • • • 3000 K (4940 F) 6600 K (11,420 F) 7900 K (13,760 F) Object cannot glow blue at any temperature. 7. Blackbody Spectrum Choose One • 10 points Note that in the above question, although the object still emits all colors of visible light, it appears blue now instead of white because of the significant difference in the intensity or amount of blue light radiated versus the amount of red light emitted. Click the + button that is to the left of the intensity scale to zoom in such that the top of the scale is at 1. Now slowly decrease the temperature from 5000K down to 300K (room temperature). Notice how the entire spectrum decreases in intensity and moves to the right into the infrared region. Even though the spectrum appears completely flat, objects at room temperature and below also emit their own light. If our eyes could detect infrared light, we would be able to see in the dark with warmer objects being brighter than others. In the introduction of this activity, we mentioned the temperature of your home on hot and cold days. Your body is kept warm in your home primarily by two ways: by direct contact with the air around you and by absorbing infrared light that is radiated from the walls. As you have seen in this activity, the light that is radiated from an object depends almost solely on the temperature of 4 the object. Based on what you have learned here, what is one reason for feeling warmer in your house on a summer day versus a winter day even though your thermostat is set the same? • • • • The walls of the house are warmer during the summer. Therefore, they radiate more infrared light that can serve to warm our body. The walls of the house are warmer during the summer. Therefore, they radiate more visible light that can serve to warm our body. The walls of the house are warmer during the summer. Therefore, they radiate more ultraviolet (UV) light that can serve to warm our body. The temperature of the walls of the house has no effect on the light they radiate. 8. Blackbody Spectrum Choose One • 10 points Since we cannot physically collect data from stars and most other objects in the universe, almost all of the information we obtain from the universe comes from analyzing the light, or spectra, from those objects.The study of light is known as spectroscopy. As we have seen in this simulation, every blackbody emits light with an easily identified pattern known as the blackbody curve. This is the particular way the total light emitted by a blackbody varies with its frequency. The exact form of the curve depends only on the body’s temperature. Since we can treat stars as blackbodies, this is incredibly useful in astronomy that shows us that the color of a star is also indicative of its temperature. Use the simulation to determine the surface temperature of the following star: Betelgeuse is a red supergiant star in the constellation Orion. Adjust the intensity scale so that the top of the scale is 31.6. Then, knowing that Betelgeuse has peak intensity in the red and infrared wavelengths, move the temperature scale up and down until you can determine the approximate surface temperature of the star. • • • • 2000 K 3500 K 7700 K 11,000 K 9. Wien's Law Choose One • 10 points The relationship between temperature and peak wavelength is given by an equation known as Wien’s Law: 5 In this equation: λ(max)= peak wavelength (cm) T = temperature (K) Based on what you have seen in the simulation and your knowledge of proportionality relationships learned this month, what is the relationship between temperature and peak wavelength? • • • • They are directly proportional. They are inversely proportional. They are exponentially proportional. They are unrelated. 10. Wien's Law Choose One • 10 points Use Wien’s Law to calculate the peak wavelength of Betelgeuse, based on the temperature found in Question #8. Note: 1 nanometer (nm) = .0000001 centimeters (cm) • • • • 6 208 nm 400 nm 828 nm 1800 nm
1. Scientific Notation Choose One • 5 points Because quantum mechanics is physics that describes the interactions of very small objects (i.e. molecules, atoms, and electrons), this week you will need to know how to multiply very small numbers. Remember that scientific notation writes very small or large number in terms of powers of 10. For example, .0008 can be written in scientific notation as 8 x 10-4 or as 8E-4. The power of 10 (-4 in this case) tells you to take the number 8.0 and move the decimal 4 places to the left giving us .0008. Which is a correct representation of .000025 in scientific notation? • 2.5E-4 • 2.5E-5 • 2.5E-6 • 25E-5 2. Scientific Notation Choose One • 5 points Let’s now multiply two numbers in scientific notation using Google. Enter .0008 into Google exactly as it was written above as: We could now multiply it by .000056 by typing: Note that we have separated our two numbers by putting them inside parentheses, and the * symbol (SHIFT+8) is used as the multiplication sign. We could have done a division instead of multiplying by separating the two numbers by a forward slash Multiply the number 4.48E-8 by 5.2E-4 using Google. What is the correct answer in scientific notation? • 6.78E-11 • 3.33E-12 • 2.40E-12 • 2.33E-11 3. Electron Transitions Choose One • 5 points As mentioned in this week’s notes on page 4, the electrons of an atom can occupy different energy shells within the atom (similar to how the planets all occupy different orbits around the Sun). Electrons prefer to be in the lowest energy shell possible (the ground state); however, they can gain energy and jump to a higher shell by absorbing light or being excited by an electric current. In accordance with the conservation of energy, if an electron drops from a higher energy level to a lower one, this must emit a photon (particle of light) with energy equal to the energy difference of the shells. A Balmer series transition is any transition of an electron from some higher energy shell down to the second lowest energy shell (n=2) in hydrogen. Looking at image (b) above, what is the wavelength of a photon emitted during the Balmer transition from the n=3 shell in hydrogen? (remember nm is short for a nanometer, for example 656 nm = 656 x 10-9 meters) • 656E-9 meters • 486E-9 meters • 434E-9 meters • 410E-9 meters 4. Momentum Choose One • 5 points Use the momentum equation for photons found in this week's notes, the wavelength you found in #3, and Plank’s constant (6.63E-34) to calculate the momentum of this photon: • 1.0E-27 kgm/s • 1.8E-27 kgm/s • 2.0E-27 kgm/s • 3.0E-27 kgm/s 5. Frequency Choose One • 5 points Use the equation from week 3: frequency=wavespeedwavelength and the wavelength you found in #3 to calculate the frequency of this photon (remember the speed of light is 3E8 m/s): • 7.6E14 Hz • 6.0E14 Hz • 4.6E14 Hz 6. Energy Choose One • 5 points Use the energy equation from this week’s notes, your answer from #5, and Plank’s constant(6.63E-34) to find the approximate energy of this photon: • 4.8E-19 Joules • 3.0E-19 Joules • 3.0E-17 Joules • 1.21 Gigawatts 7. Atomic Spectra Choose One • 5 points A glass tube is filled with hydrogen gas. An electric current is passed through the tube, and the tube begins to glow a pinkish/purple color (this is how fluorescent bulbs and neon signs produce light). If you were to pass this pink light through a prism to separate the individual light frequencies, you would see that this pink light is composed of four distinct colors: violet, green, blue, and red. Notice the similarity between image (b) above and image (b) from question #3. Which is the best description of why this occurs? • The electrons within the hydrogen atoms gain energy from the current causing them to jump to higher energy orbitals. When they fall back to a lower energy orbital they release a single proton. These protons have discrete energies equal to the difference in energy of the two orbitals. • Atoms contain continuous energy orbitals, meaning that the light the hydrogen atoms produce can be of any energy. Depending on the type of prism used, when the light reaches it, the prism will only allow specific light energies (frequencies) to pass through. • The light spectrum from any source contains all colors (frequencies) because the Planck, constant, h, is so small. 8. Momentum and Energy Choose One • 5 points The lights used by Mark Watley (played by Matt Damon) during the film The Martian seem to be Metal Halide lamps. Metal Halide lamps are filled with vaporized mercury and metal-halogen compounds. When an electric current is passed through the lamp, the tube begins to glow a bright white/blue color. If you were to pass this light through a prism to separate the individual light frequencies, you would see a rainbow just as you would if using natural sunlight because of the complexity of the metal halide gas and the vast amount of possible electron transitions. (The study of light in this way is known as spectroscopy and allows astronomers to know exactly what atoms compose distant stars, simply by looking at the light they emit. The spectral lines an atom produces uniquely identifies that atom just like a fingerprint uniquely identifies a person. The momentum equation and energy equation that we have used above can be combined to give the following equation: c=Ep where again p is the phonon momentum, E is the photon energy and c is the speed of light. When you divide the photon energy found in #6 by the photon momentum found in #4, do you get the speed of light? (If not, check your work for questions #4 through #6). • Yes • No 9. Light Choose One • 5 points All visible light (light that our eyes can detect) has wavelength between 400-700 nanometers. Wavelengths just smaller than 400 nm are Ultraviolet light. Wavelengths just larger than 700 nanometers are infrared light. What type of light is the Balmer series light that we have consider so far? • Visible • Ultraviolet • Infrared 10. Light Choose One • 5 points The solar panels used by Mark function because of the photoelectric effect. Light shines on the cells causing electrons to be ejected from the metal, which produces an electric current. At night on Mars, no light will fall on the solar cells and no electric current will be generated. According to your notes, what type of light is typically needed to cause the photoelectric effect? • Visible • Ultraviolet • Infrared 11. Balmer Series Choose One • 5 points If we were to illuminate them only with light from the Balmer transition considered above, would the solar panels produce a current? • Yes • No 12. Balmer Series Choose One • 5 points Starting with only the Balmer series light (visible light), how could we ensure that the solar panels generate a current that Mark can use for his power station? (It may help to look at the electromagnetic spectrum from week 3): • By gradually increasing the brightness (amount) of light that we shine on it. • By gradually increasing the frequency of the light we shine on it. • By gradually increasing the wavelength of the light that we shine on it. 13. Special Relativity Choose One • 5 points Imagine you are riding on a yacht in the ocean and traveling at 20 mph. You then hit a golf ball at 100 mph from the deck of the yacht. You see the ball move away from you at 100mph, while a person standing on a near by beach would observe your golf ball traveling at 120 mph (20 mph + 100 mph). Now imagine you are aboard the Hermes spacecraft traveling at 0.1c (1/10 the speed of light) past Mars and shine a laser from the front of the ship. You would see the light traveling at c (the speed of light) away from your ship. According to Einstein’s special relativity, how fast will a person on Mars observe the light to be traveling? • 0.1c (1/10 the speed of light) • c (the speed of light) • 1.1c (c+0.1c) 14. Stellar Evolution Choose One • 5 points Note: The following questions are unrelated to the Balmer series or The Martian. Please refer to your course notes. A Sun-sized star will spend most of its lifetime as a: • White Dwarf • Red Giant • Protostar • Main-Sequence Star 15. Stellar Evolution Choose One • 5 points Our Sun will eventually: • explode in a supernova. • become a white dwarf star. • become a black hole. 16. Stellar Evolution Choose One • 5 points A main sequence star does not expand or contract due to the balance between the internal heat pushing outward and the weight of the material pressing inward due to gravity. This state of maintaining a constant size is known as: • hydrostatic equilibrium • thermal equilibrium • dynamic equilibrium 17. Stellar Remnants Choose One • 5 points Neutron stars are: • Low density star remnants with many neutrons, which mass is less than the mass of the Sun. • Incredibly small remnants of super massive stars where the gravitational collapse is stop by neutron degeneracy. • Incredibly big and massive star remnants which expelled all its neutrons in a supernova explosion. 18. Stellar Remnants Choose One • 5 points Black holes are: • Star remnants from super massive stars which gravitational collapse can not be halt by electron or neutron degeneracy and gravity is so strong in their vicinity that not even light can escape. • Regions of the universe with space empty of matter or radiation that becomes so dark that forbids us from investigating it. • Regions of space where matters is not sufficiently hot to radiate in the visible spectrum. 19. Newton vs. Einstein Choose One • 5 points Which of the following states that all matter tends to "warp" space in its vicinity and that objects react to this warping by changing their paths? • Newton's Universal Law of Gravitation • Einstein's General Relativity • Einstein's Special Relativity • Newton's First Law of Motion 20. Quantum Mechanics Choose One • 5 points Wave-particle duality tells us that wave and particle models apply to all objects whatever the size, so why don't we observe wave properties in macroscopic objects? • Because their particle properties forbid us from observing their wave properties. • Because their wavelength is extremely long (undetectable). • Because their wavelength is extremely short (undetectable).

Tutor Answer

Paco369
School: UCLA

Attached.

Answers

1. 2.5 E-5
2. 2.33 E-11
3. 656 E-9
4. 1.0 E-27
5. 4.6 E 14 hz
6. 3.0 E -...

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Anonymous
Tutor went the extra mile to help me with this essay. Citations were a bit shaky but I appreciated how well he handled APA styles and how ok he was to change them even though I didnt specify. Got a B+ which is believable and acceptable.

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