I wanted to experiment and see under what conditions I would see a beam of light. I decided to go outside at night in the dark with two different flahslights.
First, I turned on an off-brand flashlight. When I shone it on the ground it made a circle shaped like an egg. There was a spot that was brightest towards the bottom middle of the egg shape. The light got dimmer as it went out from that center bright spot until the ground was not illuminated. I think there was a brighter center because the light from bulb in the flashlight was shining directly on that spot. I think the light becoming dimmer and dimmer towards the outside is due to the mirrors in the flashlihght. I think the light from the bulb in the flashlight reflects off of the mirrors in the flashlight and onto the ground. Since it is reflected light, it is not as bright as that center light that is direct from the bulb. When I shone this light up into the sky, I did not see anything. I was shocked by this and a bit disappointed that I did not see a beam.
Next, I used a bigger Mag-Lite flashlight. When I shone it on the ground it made a similar egg shaped circle onto the ground. The egg shape was bigger and brighter. I think this is because it was a bigger flashlight with a stronger current/light. When I shone the flashlight up into the sky, I saw a beam! The beam was smaller than I thought it would be. Holding the flashlight (pointed upward to the sky) while looking up into the sky, the beam looked like a cylinder. I could see the beam for a little distance but couldn't see a bright circle in the sky, like I did when I shone the flashlight on the ground. I also saw a very small number of particles in the beam. I am not sure what the particles were. They might have been dust. When someone else held the flashlight and I looked from the side, I could not see the beam. But if I stood behind them and looked up into the sky, I could see the beam.
I am not sure as to why there was a beam outside with the Mag-Lite but not in the box experiment we did in class. I am positive that the reason there was not a beam with the off-brand flashlight is because it was not a strong enought light. A possible reason for the beam with the Mag-Lite could be that there was moisture in the air and the light reflected off of it. Another possibility could be that it is darker outside than it was in the box.
Totally cool. Your descriptions of what you did and what saw are really helpful for me as a reader. I'm also noticing that you have a bunch of ideas to begin explaining what you saw:
ReplyDeleteOne idea seems to be that the bright spot in the center of the circle (on the ground) is from the direct light from the bulb, and the dimmer areas are the reflected light off the mirror. This makes sense with your idea from class two Wednesday's ago that reflected light should be dimmer than direct light. To me, this sounds like a more specific theory about what the mirror is doing than we've heard before. Maybe in your notebook you could draw a sketch of how you think this works?
It makes me wonder what Sarah P. would think, because she wrote in her paper that she didn't think that reflected light would always dimmer, especially off a mirror. Sarah? You around to weigh in?
You also seem to be saying that your experiment still allows us to have several ideas about the beam situation. You seem confident that brightness was a factor, but you also say it could also be moisture and darkness. I can't wait until others start posting about what they did to see if it helps us sort more of it out.
I'm curious, in class with the box experiment, did you look at the beam from the vantage point of the light? It sounds like you only saw your maglight beam at night when you were holding it, not when your friend was holding it away from you.
ReplyDelete-Andy (physics professor at Hamline University in St. Paul, MN and friend of Brian's)
After reading your post, I took my flashlight into my bathroom and turned off all the lights (it was very dark) and I held the light so it was facing the ceiling in hopes I'd see a beam like you did. Holding it that way made no difference, because there still was not a beam. My flashlight light is a little bit bigger but slightly dimmer than the one we used in class. I didn't notice an egg shape like you are describing, but more of a circle. Now the question I have for you is How much bigger was the mag light compared to the first flashlight? I think with theses experiments it has been proven that the moisture/ things in the air for the light to travel through doesn't matter, but it all depends on the wattage/power of the flashlight.
ReplyDeleteKimberly,
ReplyDeleteMy findings were pretty similar to yours. Even though I didnt have two different types of flashlights, I saw what you saw with the off-brand flashlight. It seems odd to me that when you stood to the side of the beam it wasnt visible, but from behind you could see it. Do you think this was because absolutly no light from the flashlight was coming in your direction? Great tests and observations!
Thanks everyone for your comments!
ReplyDeleteAndy, with the box experiment in class I only looked in from the side of the box, not from the vantage point of the light. The original scenario was to imagine we were looking into a hallway from a side door. At the end of the hallway is someone holding a flashlight.
Ashley, the MagLlite was a lot bigger than the first flashlight I used. I'd say almost twice as big. And I could tell the light was brighter/stronger. Going in the bathroom was a really good idea. I think it would be a good really dark place. I was trying to find dark places in my apartment but it was difficult with the windows.
Chelsey, I do not think a lack of light coming in my direction was the reason I was unable to see a beam from the side. Because, when I actually did see the beam I was standing behing the flashlight so there was no light coming my direction then either.