20 question quiz
QUESTION 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? 1. 2.5E-4 2. 2.5E-5 3. 2.5E-6 4. 25E-5 QUESTION 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? 1. 6.78E-11 2. 3.33E-12 3. 2.40E-12 4. 2.33E-11 QUESTION 3 Electron Transitions Choose one • 5 points 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) 1. 656E-9 meters 2. 486E-9 meters 3. 434E-9 meters 4. 410E-9 meters QUESTION 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 Planck’s constant (6.63E-34) to calculate the momentum of this photon: 1. 1.0E-27 kgm/s 2. 1.8E-27 kgm/s 3. 2.0E-27 kgm/s 4. 3.0E-27 kgm/s QUESTION 5 Frequency Choose one • 5 points Use the equation from week 3: frequency=wavespeed/wavelength and the wavelength you found in #3 to calculate the frequency of this photon (remember the speed of light is 3E8 m/s): 1. 7.6E14 Hz 2. 6.0E14 Hz 3. 4.6E14 Hz QUESTION 6 Energy Choose one • 5 points Use the energy equation from this week’s notes, your answer from #5, and Planck’s constant (6.63E-34) to find the approximate energy of this photon: 1. 4.8E-19 Joules 2. 3.0E-19 Joules 3. 3.0E-17 Joules 4. 1.21 Gigawatts QUESTION 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? • • • QUESTION 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=E/p 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). 1. Yes 2. No QUESTION 9 Light Choose one • 5 points All visible light (light that our eyes can detect) has a 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 considered so far? 1. Visible 2. Ultraviolet 3. Infrared QUESTION 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? 1. Visible 2. Ultraviolet 3. Infrared QUESTION 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? 1. Yes 2. No QUESTION 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): 1. By gradually increasing the brightness (amount) of light that we shine on it. 2. By gradually increasing the frequency of the light we shine on it. 3. By gradually increasing the wavelength of the light that we shine on it. QUESTION 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 nearby 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? 1. 0.1c (1/10 the speed of light) 2. c (the speed of light) 3. 1.1c (c+0.1c) QUESTION 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: 1. White Dwarf 2. Red Giant 3. Protostar 4. Main-Sequence Star QUESTION 15 Stellar Evolution Choose one • 5 points Our Sun will eventually: 1. explode in a supernova. 2. become a white dwarf star. 3. become a black hole. QUESTION 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: 1. hydrostatic equilibrium 2. thermal equilibrium 3. dynamic equilibrium QUESTION 17 Stellar Remnants Choose one • 5 points Neutron stars are: 1. Low density star remnants with a mass less than the mass of the Sun. 2. Incredibly small remnants of supermassive stars where the gravitational collapse is halted by neutron degeneracy. 3. Incredibly big and massive star remnants that expel all neutrons in a supernova explosion. QUESTION 18 Stellar Remnants Choose one • 5 points Black holes are: 1. Star remnants from supermassive stars in which gravitational collapse can not be halted by electron or neutron degeneracy, and gravity is so strong in their vicinity that not even light can escape. 2. Regions of the universe with space empty of matter or radiation that become so dark that they forbid us from investigating them. 3. Regions of space where matter is not hot enough to radiate in the visible spectrum. QUESTION 19 Newton vs. Einstein Choose one • 5 points Which