Chapter 5
15. How do we convert a continuous spectrum shown as a band of light (like a rainbow) into a graph of the spectrum?
Through spectroscopy. And then changing them from showing only visible light to showing the amount of radiation, or intensity, at each wavelength.
31. A "white hot" object is hotter than a "red hot" object.
True. An object must emit a red color from heat before it can emit a white color, because white is all of the colors combined.
25. The walls of my room are transparent to radio waves.
True. The fact that the walls are transparent to radio waves means that they would allow the radio waves to enter into the room, which is an accurate statement.
20. Describe two ways in which the thermal radiation spectrum of an 8,000K star would differ from that of a 4,000 K star.
-An 8,000K star would emit a lot more light at every wavelength than the 4,000K- sometimes in places where the cooler star wont emit light at all-making it bluer. (shorter wavelengths). -Hotter star emits photons with a higher average KE (makes the peaks of the graph at shorter wavelengths for hotter objects).
4. What is a spectrum and how do we see one?
A spectrum, more specifically an electromagnetic spectrum, is a scale of wavelengths of different types of light-even those we cannot see. The Visible Light section (which is the only part we can see) is only a tiny, tiny portion of the whole spectrum.
16. Explain the atomic structure of the atom. Tell how this creates the distinctive patterns of emission and absorption spectra.
An atom consists of protons, neutrons, and electrons. Protons and Neutrons are found in the nucleus in the center of the atom, while electrons surround the nucleus. The electron collisions sometimes transfer just the right amount of energy to change energy levels causing the lost energy to emit a photon of light. This happens in moderately warm gas clouds. When atoms absorb photons with the right amount of energy needed to raise an electron from a lower to a higher energy level, that create the distinctive patterns of the absorption spectra. Basically, light produces a continuous rainbow, but hydrogen atoms get in the way and absorb light at specific wavelengths.
10. Briefly describe the structure of an atom. How big is an atom? How big is the nucleus in comparison to the entire atom?
Atoms come in different types, and each type corresponds to a different chemical element, protons neutrons and electrons make it up, and P and N make up the nucleus; The nucleus is almost 100,000 times smaller than the atom.. BUT it contains almost all of its mass (since P & N are 2000x more massive than electrons).
17. Describe the conditions that would cause us to see each of the three basic types of spectra. What do we see in the Sun's spectrum shown on the opening page of this chapter?
Continous: light bulb produces light of all colors Ex. Incandescent light bulb Emission Line: gas cloud emits light at specific colors depeding on its composition and temperature Absorption Line: Light from a hot source passes through a cooler gas cloud (which absorbs certain wavelengths [colors])
12. What is electrical charge? Will an electron and a proton attract or repel one another? Will two electrons attract or repel one another? Explain.
Electrical charge is a fundamental property that describes how strongly an object will interact in electromagnetic fields. Protons and electrons would attract, but electrons and electrons would not attract.
14. What do we mean when we say that energy levels are quantized in atoms? Under what circumstances can energy level transitions occur?
Electrons have quantized energy levels in all atoms, not just in hydrogen. Quantized means that they are sudden changes with no in-between level. Energy level transitions can occur only when an electron gains or loses the exact amount of energy that separates two energy levels.
5. Give an example from everyday life of each of the four major types of interaction between matter and light.
Emission: light bulb emits visible light Absorption: hand absorbs light if its near a light bulb Transmission: glass and air transmit light Reflection: light can bounce off matter and go in different directions
33. Galaxies that show redshifts must be red in color.
False. For distant galaxies, the light spectrum is wrong. The frequency lines of the spectrum are all too low. One possible explanation of the incorrect spectrum is that those stars and galaxies are moving away from us, and that the spectrum is shifted toward the red end of the color spectrumm because of the Doppler effect.
28. If you had X-ray vision, you could read this entire book without turning any pages.
False. If you were using x-ray vision, you would not be able to resolve the letters on individual pages.
29. Two isotopes of the element rubidium differ in their number of protons.
False. Isotopes of the same element must differ in the number of neutrons, not protons. If the isotopes differed in the number of protons, they would be completely different elements.
30. If you could view a spectrum of light reflecting off a blue sweatshirt, you'd find the entire rainbow of color.
False. You would see only blue coloring. Blue objects absorb all of the colors of the rainbow other than blue.
18. How can we use emission or absorption lines to determine the chemical composition of a distant object?
Hydrogen emits and absorbs light at specific wavelengths, therefore if youre looking at a distant cloud that produces a certain spectrum (w/ certain absorption lines), you can know its made of hydrogen. Each chemical and its ions leave different "fingerprints."
22. Describe each of the key features of the Martian spectrum and explain what it tells us about the object.
Key features of the martian spectrum include the dashed line of the continuous spectrum (caused by the Sun's reflected light), the high intensity of the scattered red light (tells us the chemical composition of Mars-its blue), the peak in the thermal radiation is in the infrared (tells us its much cooler than the Sun), emission lines in the UV (tells us Mars' atmosphere contains hot gas at high altitudes), absorption lines (tells us about CO2 in the atmosphere), and the Doppler Effect (towards red means Mars is moving away and towards Blue means towards us)
8. What is a photon? In what way is a photon like a particle? In what way is it like a wave?
Light behaves as both a wave and a particle, light comes in individual pieces called photons. Particle: photons of light can be counted individually. Wave: each photon is characterized by a wavelength and frequency
7. What do we mean when we say that light is an electromagnetic wave?
Light waves are traveling vibrations of both electric and magnetic fields
11. What determines an atom's atomic number? Under what conditions are two atoms different isotopes of the same element? What is a molecule?
Number of protons, different isotopes because of different number of neutrons, molecules are formed when multiple atoms combine
3. Think of three very different ways I could create the red light for the demonstration above.
Shine a red lightbulb, a white lightbulb with a red film piece over it, or put a red bottle top on the end of a flashlight. Basically this would work because you absorb all of the other colors except red. OR. Produce an emission line of only red light w/ for example, a laser. Purpose of this is because red light does not affect your night-vision.
23. Describe the Doppler effect for light and what we can learn from it. What does it mean to say that radio waves are blue shifted? Why does the Doppler effect widen the spectral lines of rotating objects?
The Doppler Effect is when the wavelengths of spectral lines are slightly shifted depending on the velocity of the light and whether it is moving towards or away from us as it orbits the Sun. Blue-shifted (closer together) radio waves means the object is moving towards us. The Doppler effect widens the spectral lines of rotating objects because the wavelengths changes from blue or red. Blue-shifted, red-shifted, and non-shifted photons mix together to get how its rotating.
1. What is this? What are the dark lines?
The picture is of an Absorption Line Spectrum, which is when a cloud of gas lies between a hot light source and us. Specifically, this picture is showing the Sun's visible light spectrum (but in great detail). The dark lines are called absorption lines, which are where the cloud absorbs specific wavelengths, or colors, of light leaving a spot with a drop of wavelength intensity. The "clouds" in this picture are the Sun's visible surface called the "photoshere."
19. How do the properties of light allow us to determine the physical properties of stars?
The properties of light allow us to determine the physical properties of stars mainly by temperatures. The first law of thermal radiation states that each square meter of a hotter object's surface emits more light at all wavelengths. The second law states that hotter objects emit photons with a higher average energy. Use the absorption spectrum to find chemical composition. Blue stars are hot and red stars are cool.
34. If a distant galaxy has a substantial redshift (as viewed from our galaxy), then anyone living in that galaxy would see a substantial redshift in a spectrum of the Milky Way Galaxy.
True. The increasing distance between the two galaxies will red shift light traveling between them in either direction.
27. If you could see infrared light, you would see a glow from the backs of your eyelids when you closed your eyes.
True. The infrared light would be able to penetrate through my eyelids because they are not completely opaque to wavelengths.
32. If the Sun's surface became much hotter (while the Sun's size remained the same), the Sun would emit more ultraviolet light but less visible light than it currently emits.
True. When heat increases, so does the frequency and energy of the wavelengths. Because of this, some visible light would be converted to ultraviolet light.
26. Because of their higher frequencies, X rays must travel through space faster than radio waves.
True. X-rays have both a higher energy and frequency, and therefore will travel through space faster than radio waves.
13. Describe the phase changes of water as you heat it starting from its solid phase, ice. What happens at very high temperatures? What is a plasma?
Water will be in a solid from as ice and as it heats up it becomes a liquid form known as water. When it obtains enough energy it will become its gaseous form through a process called evaporation. A plasma is a type of hot gas in which atoms have ionized. Because a plasma contains many charged particles, its interactions with light are different from those of a gas consisting of neutral atoms, which is one reason that plasma is sometimes referred to as "the fourth phase of matter". ex's. solid=desk, liquid=beer, gas=nitrogen, plasma=fluorescent lights
6. Define wavelength, frequency, and speed for a wave.
Wavelength: distance from one peak to the next Frequency: number of peaks passing by any point each second Speed for a wave: how fast the peaks travel across the pond
2. On a very strange whim I have painted my windowless room blue [450nm] with a white ceiling and a black floor. I turn on a red [650nm] light. What do I see? What if I had a detector sensitive to the infrared?
You would see a red ceiling, a black floor still, and your walls would still appear black because a blue wall reflects only blue light and absorbs all others, (but since there's no blue photons, they cant reflect) which means it If you had a detector, the whole thing would be red.
9. List the different forms of light in order from lowest to highest energy. Would the list be different if you went in order from lowest to highest frequency? From shortest to longest wavelength? Explain
wavelength: gamma, x-rays, ultraviolet, visible, infrared, microwave, radio No, it would be the same if it were organized by frequency Yes, they would be backwards if they were organized by wavelength because the ones with higher frequency and energy have a shorter wavelength.