## Physics Experiment Ideas

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mud
Posts: 18
Joined: Thu Dec 20, 2007 2:06 am UTC

### Physics Experiment Ideas

I'm currently doing high school physics and I'm trying to think of an experiment that I could easily do at home. Seeing as most of the posts in the Favourite Home Experiments topic are about blowing things up, I was wondering if I could ask for any suggestions here.

Examples of other pracs we've done in class: heat capacity of water, the flight of a rubber band (seriously), an experiment to attempt to find planck's constant.

Basically I just need an experiment to test some variable.

Also, it's already been suggested to me to try Young's Double Slit experiment, so I might try that - if anyone has any hints on how to do it best at home, I'd be glad to hear.

Thanks (:

idobox
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Location: Marseille, France

### Re: Physics Experiment Ideas

You need the most powerful laser you can find, and cardboard. A shoebox is a good starting point.

You then need to add 2 more walls inside the box.
On the first one, you poke a small hole with a needle. That will behave as a spatial filter and diffractor.
On the second one, you cut slits with an exacto knife. Make sure they are vertical, and don't cut touch the border of the wall, otherwise it will lose it's rigidity.
You don't need them to be very thin.

Finally, you shoot the laser into the needle hole. If the diffraction cone is not large enough, you can add a lens between the needle hole and the slits.
To see anything, you will need to be in complete darkness.
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Charlie!
Posts: 2035
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### Re: Physics Experiment Ideas

idobox wrote:You need the most powerful laser you can find, and cardboard.

Note that this advice doesn't apply to you if you can find a laser that puts out more than 5 milliwatts
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PM 2Ring
Posts: 3707
Joined: Mon Jan 26, 2009 3:19 pm UTC
Location: Sydney, Australia

### Re: Physics Experiment Ideas

Since we're talking about diffraction, I have to mention
studyphysics wrote:You can actually do the single slit experiment wherever you are right now! Hold two of your fingers very close together; there should be only the tiniest little gap between them that you can barely see through. Look towards a light source, like a light bulb, through the gap in your fingers. In the gap between your fingers you shold see very faint gray lines that run parallel to your fingers... these are the destructive interference "dark" fringes!

mercuryseven
Posts: 207
Joined: Mon Nov 23, 2009 8:36 am UTC

### Re: Physics Experiment Ideas

Measure the acceleration of gravity using a simple pendulum? Or is that too easy?

The laser idea is good, since any good and cheap laser pointer may work (nowadays they are sold as key chains!) You may be able to measure the wavelength of the laser.

Atwood
Posts: 3
Joined: Wed Jul 21, 2010 4:36 pm UTC

### Re: Physics Experiment Ideas

PM 2Ring wrote:Since we're talking about diffraction, I have to mention
studyphysics wrote:You can actually do the single slit experiment wherever you are right now! Hold two of your fingers very close together; there should be only the tiniest little gap between them that you can barely see through. Look towards a light source, like a light bulb, through the gap in your fingers. In the gap between your fingers you shold see very faint gray lines that run parallel to your fingers... these are the destructive interference "dark" fringes!

That's pretty cool, I'll have to teach it to some students some time. Science!

mercuryseven
Posts: 207
Joined: Mon Nov 23, 2009 8:36 am UTC

### Re: Physics Experiment Ideas

I'm not sure whether you're still looking for ideas, but I came across an interesting io9 article about How to Measure the Speed of Sound

nash1429
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### Re: Physics Experiment Ideas

Atwood wrote:
PM 2Ring wrote:Since we're talking about diffraction, I have to mention
studyphysics wrote:You can actually do the single slit experiment wherever you are right now! Hold two of your fingers very close together; there should be only the tiniest little gap between them that you can barely see through. Look towards a light source, like a light bulb, through the gap in your fingers. In the gap between your fingers you shold see very faint gray lines that run parallel to your fingers... these are the destructive interference "dark" fringes!

That's pretty cool, I'll have to teach it to some students some time. Science!

I can only get one line on each finger, and I think it might just be that blind spot you get from looking at bright lights. Any tips?

PM 2Ring
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Location: Sydney, Australia

### Re: Physics Experiment Ideas

nash1429 wrote:I can only get one line on each finger, and I think it might just be that blind spot you get from looking at bright lights. Any tips?

It can be a bit tricky at first, but it's easier with practice. Maybe try it with a less bright light source, so you don't get such after-image effects. I get pretty good results looking at a white area on my computer's LCD monitor (like this reply box). It also helps if you close the other eye.

The gap should be around 0.5mm or less, with the sides of the gap as parallel as possible. I usually do it with my index & middle fingers, or middle & ring fingers, with my hand 20-30cm from my face, looking through the gap between the top joint & second joint. But I can also do it using the index fingers of both hands; it is rather difficult to keep the gap steady with this method, but I can get 3 or 4 "shadow" lines that way. I just tried it with the index finger of my right hand wedged between the index & middle fingers of my left hand, and that worked pretty well, too.

As with many phenomena, it's easier to see once you know what you're looking for. So maybe try to do it with a more stable gap, for example, a pair of knife blades held edge to edge. A pair of razor blades clamped together (either edge to edge or face to face) makes an excellent slit.

Good luck, and if all else fails, consider getting an eye test. But if your eyes can focus at close distance well enough to read, you should be able to see these interference lines.

eternauta3k
Posts: 519
Joined: Thu May 10, 2007 12:19 am UTC
Location: Buenos Aires, Argentina

### Re: Physics Experiment Ideas

Something I'd like to do is a spinning top with two little weights inside capable of moving radially. You'd set it spinning with the weights far from the center, and after some time a mechanism pulls them in. Thanks to conservation of momentum, it should speed up.

It's not so fancy, but if the insides are hidden it would look like it sped up all on its own.
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