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Module 1, Assignment 1
Describe the light sources and spectra that you have projected in detail as well as any experimental difficulties you encountered in the process. How do the different light sources compare with each other?
Assignment 1
ReplyDeleteLooking at different light sources through the diffraction grating
Fluorescent lights
Red and green very little blue
Sun light
ROYGBIV
Incandescent light bulb
ROYGBIV
Pen flash light from Wal-Mart
ROYGBIV
Laser pen light from Wal-Mart
630-650 nm
Bright red
Didn’t use spectrometer
Used diffraction grating 530 grooves/mm and saw interference dots at 5° and 15°.
I foyund it difficult to see the differences between the ful spectrum results. Also the results from my fluorescent lights changed. I was surprised they had no blue element.
This assignment is interesting in that it depends on the wave nature of light. Meanwhile the CCD cameras that telescopes use depend upon the particle/photon behavior of light. If we let one photon at a time hit the diffraction grating would we still see interference patterns. The answer is yes. Which slit did the photon go through? As soon as we try to find out the diffraction/spectrum disappears. Such is the strangeness of quantum theory
Very similar to Barry, using the spectroscope to view sources of light is fun - interesting. We use these to view atomic emmission spectra from gas filled tubes, and then use our illustrations to identify unknown gases (based on wavelengths emitted).
ReplyDeleteHowever, the most fun we had with this project was the holographic diffraction grating that produced a continuous spectrum. I allowed the students (juniors and seniors) to set up the apparatus and they did a great job 1st time. The grating was set up with the spectrum projecting vertical, so they turned the grating 90 degrees and saw the two specra on the white board. Then we shut the lights off.
We projected it onto the dry erase board for my physics class and then used different different colored markers to show how each light gives each color of marker a different appearance.
Then the real fun came using the colored filters to limit the light rays entering the diffration grating. The students loved seeing that blue only allowed blue waves through and red only allowed red - but that the mixture of using red and blue filters allowed no light through. The yellow limited the rays but still seemed to allow all colors through and the green still allowed some blue through.
Next we will explore the polarity of light, with polarization filters.
First off, I used the spectroscope to make my observations, because I don’t really see any changes with the diffraction grid when I am looking at different light sources.
ReplyDeleteLooking at the incandescent light bulb in my overhead I saw a continuous spectrum, all colors of the rainbow present. I also saw what looked like a continuous spectrum when looking at sunlight reflected off of white paper, but I *know* it should be an absorption spectrum. I’m guessing the dark lines are too narrow to see without a microscope or an enlarged spectra. The fluorescent lights in my classroom have a bright green and purple emission line superimposed over a continuous background spectrum. Perhaps similar to what you might see when looking at a spectral discharge tube?
Next I tried to look at red and blue lasers. The blue laser showed the blue and green part of the spectrum but the red laser only showed the red part of the spectrum. There was a very faint continuous spectrum in the background as well, which I am thinking is the daylight coming in from the windows when I looked at the laser lights.
My computer monitor was pretty interesting. It does not give off light at all wavelengths. There is a pretty significant dark band in the red region of the spectrum.
I’m having difficulties with the diffraction grating. All I see are a multitude of rainbows everywhere.
Assignment 1
ReplyDeleteThe spectrum of colors produced by fluorescent and incandescent lights is continuous similar to rainbow. The spectrum produced by these two sources is similar to the spectrum produced by the sun. Incandescent lights transmit more red wavelengths than fluorescent light and fluorescent lights transmit more blue wavelengths. The LCD of my laptop produce a bright spectral band of ROYGV. The blue LED light of my power cord produce a bright blue color in the line of spectrum.
I spent the better part of an hour looking at light sources through my diffraction grating. I was VERY surprised to see magenta in a lot of the continuous spectra. I also noticed that I could see two spectra in most light sources. On one side of the source, I could see ROYGBIV; on the other, I would see VIBGYOR (the rainbow backwards). I was also interested that the appearance of the spectrum changed depending on what material the light passed through. For example, I looked at fluorescent lights with a plastic covering and without. With the plastic, the colors in the spectrum were more pastel and looked like stacked pages. Without plastic looked a little more like a normal continuous spectrum.
ReplyDeleteI had a little too much fun looking at light. Here were my favorites:
1) iPhone flashlight (you can set it on solid green, yellow, white, red or flashing)
Green: mostly yellow with blue
Yellow: mostly yellow
Red: mostly red
White: all colors with a white band (surprising!) in between yellow and green
Flashing: All the spectra flashed..way cool.
2) Flame: Lots of red, with a little green, then, purple. The spectrum became weak as the flame died with the wind. I know this is obvious, but it was really neat to see!
3) Cell phone: This one was a continuous rainbow. All colors seemed to be treated equally. However, like the flame, the spectrum faded as the light dimmed.
I have tried experimenting on various sources of light such as the sun, fluorescent and incandescent lights, candle, flashlight, lamp post infront of our house, moon light and even the skylight that we have in the kitchen, all of these light sources produce a spectrum of rainbow colors backward on both sides -VIBGYOR. When I looked at the chandelier it produces the same spectrum of colors but in multi dimensional arrangements, some colors are quite vivid while others are fainted. As I sat on the passengers seat, I tried looking at the signs on the streets and even the stop lights, I've seen the colors of rainbow but they varied on the degrees of clarity. I also observed that the further the source of light the thinner the spectrum of colors and as it gets closer it gets wider. It was fun doing this activity, even my husband and 5th grade daughter enjoyed it.
ReplyDeleteI used the diffrection grating - here are my observations:
ReplyDeleteSodium vapor street light – continuous spectrum, with superimposed emission lines (1blue, 2 green, 1 yellow-green, 1 faint orange, 1 red) as well as a yellow-orange absorption line that was more visible in the second order spectrum
Incandescent light – continuous spectrum
Green neon light – continuous but with large gaps – violet was visible, no blue, green, yellow and orange were visible, no red
White neon – nearly perfect continuous spectrum, though the violet was darker
Sun – very difficult to examine, with a continuous spectrum that appeared very large in the center (orange-yellow-green)
Good start, all! Do reads other's posts especially if you are having problems. Ad, if you are having trouble with the grating, try in a darken room with only one light to begin: that may help. And remember you can email Chri or me individually, just as we will sometimes work individually with you.
ReplyDeleteSee Bekkah's comment about appearance changing depending on what the light passes through: we will be exploring that concept through filters.
I started my quest for light spectrum using my study table lamp. I observed a smooth continous spectrum (rainbow color). Then I went over the storage area and observed the spectrum of fluorescent bulb..the same spectrum but it is not smooth. There are some bright lines. I went to the restroom to check for the spectrum of a lighter light. I observed the same continous spectrum. The same with the candle light. I saw some yellow lights but I dont know if it is included in the spectrum. I had some difficulties observing the spectrum of sunlight and street lights because some stray lights enter my spectrometer. I saw a continous spectrum for sunlight. I tried to look on the fraunhofer lines but I did not observe any. I also tried to observe the moonlight spectrum and it is just the same with sunlight spectrum. Maybe because the moonlight is just a reflected light from the sun???
ReplyDeleteI did the experiment last night and found out the following observations:
ReplyDeleteThe spectrum of colors produced by fluorescent and incandescent light sources wass continuous similar to rainbow with Red, orange, yellow, yellow green green, blue green, dark blue, sky blue and violet. The LCD of my TV produced a bright spectral band of Red, Orange Yellow, Green, Blue and Purple. I also used the flashlight toy of my toddler son and I only saw spectral band of Red Orange, Yellow, Green and Blue.
I noticed that for the incandescent light, there were 2 spectral band of Red, orange, yellow, yellow green green, blue green, dark blue, sky blue and violet; clearer on the upper portion and a little bit thinner on the lower portion.
Using the spectrometer, the incandescent light has a continuous spectrum with all visible colors present just like the rainbow (ROYGBIV). There are no bright lines and no dark lines in the spectrum. On the other hand, the spectrum of a fluorescent light has bright lines and also a continuous spectrum. The sunlight spectrum is also a continuous spectrum but there are some dark lines. I had a hard time describing the sunlight spectrum because I observed scattered spectrum in my spectrometer.
ReplyDeleteI looked at sunlight, light bulbs, a blue neon light, a heat lamp, and florescent kitchen light with my diffraction grating. One experimental difficulty was just learning how to use it to see a clear spectrum; I think I had it tipped the wrong way at first. Almost every light source gave me the full rainbow of colors. My florescent kitchen light was different though. I only saw four colors—a really wide yellow band, then pinkish, then blue. The heat lamp was interesting. Like the light bulbs and sunlight, I saw the full spectrum. But looking at light from the heat lamp bulb I saw these crystal clear bands all down the spectrum. They looked like lines on an earthworm. Perhaps this is because of the intensity of the light? The blue neon light was also cool. I saw all of the colors, but they were present in different parts of the light … also the shape of the light was replicated again and again. I want to find one of those laser pointers to look at so I can isolate just one or two colors. I’ve been carrying the grating around looking at different light sources—it’s really beautiful!
ReplyDeleteFrom John Webster
ReplyDeleteI looked at various light sources using the diffraction grating.
Both the incandescent and fluorescent lights produced the full spectrum of visible light from red to violet. The colors were arranged from the light source from the higher frequency/smaller λ colors to the lower frequency/larger λ colors or, Violet, Blue, Green, Yellow, Orange, and Red.
I also compared HID and Halogen headlights of my cars in my garage and saw that they both produced the full spectrum of VBGYOR from the light’s source.
I next observed the light from the 3 settings on my camping headlamp. The red LED produced only red light. I was sort of surprised that the “Blue-White” LED light did produce the full spectrum of colors, just like the incandescent light bulb.
Lastly I took the grating outside to look at the Sun. When I was looking outside at a 90° angle to the Sun and held the grating in front of me, I saw all the colors, but the red color was closest to the Sun. I could not understand why that would happen. I went out again later and viewed it in a different location and this time the order was correct. I think what must of happened on the previous day was that I was getting a reflection off my metal grill on my backyard patio.
Oh my! I have done what I get so annoyed with my students about: waiting until the last minute to post my results. Although I did a little work a couple of weeks ago, I'm still scolding myself. There are positives and negatives to this. A big negative is that everyone has beat the basic information to death. A great positive is that I've learned from others' posts and have learned lots. This learning can take place, however, after early original posts!
ReplyDeleteI had fun making the diffraction grating look like a giant slide by using an old manila folder and sandwiching the plastic grating in between.
I noticed right away that the diffraction grating has a definite top, bottom and sides (depending on how you want to define them. Like Bekkah (and others), I also noticed that I could see two spectra in most light sources. On one side of the source, I could see ROYGBIV; on the other, I saw the mirror image (the rainbow backwards).
I originally looked at several different light sources a couple of weeks ago. After reading others' posts, I went back and looked at the “common” light sources in my house and am now wondering/questioning what I originally thought as a continuous spectrum I now see what I think are lines or spaces in between colors.
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ReplyDeleteI noticed that in the case of incandescent light bulbs I saw a complete rainbow spectra when I looked at them through the diffraction grafting. LED light sources, like bike lights, have only one color inside of them. The gas discharge tubes that I looked at seemed to have many individual lines inside of them. Interestingly the florescent lights in the room had lines that looked much like the lines I saw in the Mercury light source, but they also had a faint rainbow glow, like the incandescent light bulb does. I have been told that this is because there is an extremely strong ultraviolet line that Mercury emits and that the florescent light is coated with a substance that absorbs that infrared light and reemits it across the entire visual spectra.
ReplyDelete