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, w
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 theres no blue photons, they cant reflect) which means it If you had a detector, the
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/
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.
Give an example from everyday life of each of the four major types of interaction between matter and light.
Emission: A light bulb
Absorption: Hands absorb energy from a light bulb
Transmission: Windows
Reflection/scattering: Mirrors
Define wavelength, frequency, and speed for a wave.
Wavelength: the distance from peak to peak or trough to trough
Frequency: # of peaks that pass by any point in each second
Ex. Leaf bobs 3 times/sec. Frequency= 3 cycles/sec
Speed for a wave: How fast their peaks travel. Basically, how fast the energy tra
What do we mean when we say that light is an electromagnetic wave?
Light is an electromagnetic wave b/c it is vibrations of both electric and magnetic fields caused by the motions of charged particles. (Electrons move just like the leaf on the pond)
What is a photon? In what way is a photon like a particle? In what way is it like a wave?
Photon: "pieces," or single units of light, that have properties of particles AND waves. It's like a particle b/c they can be counted individually and can hit surfaces one at a time. And they're like waves because each one is characterized by the same pro
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.
By energy from lowest to highest:
Radio, Microwaves, Infrared, Visible, UV, XRays, Gamma
Lowest to highest frequency:
SAME
Shortest to longest wavelength:
REVERSE
B/c frequency determines energy, so it's the same, and then smaller wavelengths means a high
Briefly describe the structure of an atom. How big is an atom? How big is the nucleus in comparison to the entire atom?
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. An atom is very small (specifically 10^-10 meter). The nucleus is almost 100,000 times sma
What determines an atom's atomic number? Under what conditions are two atoms different isotopes of the same element? What is a molecule?
An atom's atomic number is determined by the # of protons.
Isotopes occur when there is the same # of protons, but a different # of neutrons (giving it a different mass by same atomic number)
A molecule is when atoms of the same element combine.
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.
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?
Ice changes to liquid at the melting point; liquid changes to gas at the boiling point, At very high temperatures, sublimation (the process when molecules escape from a solid) and evaporation (when molecules escape from a liquid) occur much easier and mor
What do we mean when we say that energy levels are quantized in atoms? Under what circumstances can energy level transitions occur?
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. Level 1=0-10.2, Level 2=10.2-12.1, Level 3=12.1-12.
How do we convert a continuous spectrum shown as a band of light (like a rainbow) into a graph of the spectrum?
15. Through spectroscopy. And then changing them from showing only visible light to showing the amount of radiation, or intensity, at each wavelength.
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 energ
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 (
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 "fingerpr
How do the properties of light allow us to determine the physical properties of stars?
We can determine a star's temperature. Since temperature is just the average KE, the photons average kinetic energies matches that of the atoms or molecules in the object. This is what we call thermal radiation..which gives a thermal radiation spectrum. H
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
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 radi
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