# In need of help for Physics/Astronomy project

#### Caesars_son

Hi all! As a participant in my school's science research program, I'm required to devise a project to work on for a while. All of the other students have been guided towards something bio/comp programming related, but as my interest is in physics, I do not wish to follow them. I am having great difficulty coming up with a research project that is feasible for someone of my level of knowledge. Any recommendations?

#### jambaugh

Gold Member
With lasers so easy to get nowadays you could do a few really impressive physics demonstrations with those. You could demonstrate interference, diffraction, refraction.
You could measure the speed of light in water by carefully measuring the refraction angles of a laser beam and working out the index of refraction.
Try simultaneously producing a single slit or double slit diffraction pattern through the same slit with a red and a green laser pointer.

To make a good double slit, place a small square of aluminum foil on a hard surface, glass would be ideal. Take two thin razor blades (or take one and break it in half and use each half so the back is not sharp) and pinch them together with some small locking pliers. (Heavy forceps should work well) Then make a clean single cut with the pair on the foil. You will get two parallel cuts with a reasonably uniform separation. You want to carefully frame the foil. Pulling on it could distort the slits.
[EDIT: I don't need to say be very very careful here, try using pliers to handle the blades since it's so easy to slip and cut yourself here.]

Hmmm... what else? Well you could make a good pendulum (use a rod, not a flexible cord or string), and demonstrate how its period is not quite the same when it swings wider... (the general rule is you can treat a pendulum as a simple oscillator with amplitude independent frequency provided its swing is below 10 degrees).
You will want to make it sturdy and very low friction so that it swing for a long time at higher amplitude.. you can then get a more precise frequency by counting many many swings over a long time. Compare the frequencies when it swings below 10 degrees with when it swings greater than 15 or 20 degrees. Do many measurements and average the results to improve precision. Here's a link to the math...
Large Angle Pendulum Formula

There's a demonstration I do in my math classes to show the sum to product, product to sum trigonometry formulas in action. Beat frequencies and audio interference. You can download free apps that will produce sine waves of given frequencies and phased out of the stereo channels of your mobile device. (Search for "Signal Generator" apps.)

To demonstrate beat frequencies just output two frequencies differing only by a small amount, say 2 Hertz, you will then hear the tone warble at the difference in frequencies.

To do an interference experiment you can then output the two sound channels to a pair of speakers with a specific distance between them (you'll want to do this outside away from any walls or objects that might reflect the sound, say on a card table in the middle of a football field.) Then walk around the them a good distance away and notice in which directions the sound is loudest and in which is least loud. Do this with different frequencies and/or different speaker separation and also with different phase relationships between the two sources if you have an app that lets you control that. This is basically a sound version of the double slit interference experiment.

The math requires the wavelength of the sound which is related to the frequency by the speed of sound. You can thereby use the interference to actually calculate the speed of sound. You might even try comparing the results for different times of day when the air temperature and humidity have changed and see if you can detect a difference.

If you want to get really wild you could combine the beat frequency and interference experiments by outputting slightly different frequencies to the two speakers, you should then observe a moving interference pattern that cycles at the difference in frequency.

Well there are a few I could come up with off the top of my head. I hope they help or at least stimulate your imagination enough to find your own experiments. I don't know your age/school level but I hope I gave enough variety to let you pick a degree of advancement suitable to your level.

#### Caesars_son

With lasers so easy to get nowadays you could do a few really impressive physics demonstrations with those. You could demonstrate interference, diffraction, refraction.
You could measure the speed of light in water by carefully measuring the refraction angles of a laser beam and working out the index of refraction.
Try simultaneously producing a single slit or double slit diffraction pattern through the same slit with a red and a green laser pointer.

To make a good double slit, place a small square of aluminum foil on a hard surface, glass would be ideal. Take two thin razor blades (or take one and break it in half and use each half so the back is not sharp) and pinch them together with some small locking pliers. (Heavy forceps should work well) Then make a clean single cut with the pair on the foil. You will get two parallel cuts with a reasonably uniform separation. You want to carefully frame the foil. Pulling on it could distort the slits.
[EDIT: I don't need to say be very very careful here, try using pliers to handle the blades since it's so easy to slip and cut yourself here.]

Hmmm... what else? Well you could make a good pendulum (use a rod, not a flexible cord or string), and demonstrate how its period is not quite the same when it swings wider... (the general rule is you can treat a pendulum as a simple oscillator with amplitude independent frequency provided its swing is below 10 degrees).
You will want to make it sturdy and very low friction so that it swing for a long time at higher amplitude.. you can then get a more precise frequency by counting many many swings over a long time. Compare the frequencies when it swings below 10 degrees with when it swings greater than 15 or 20 degrees. Do many measurements and average the results to improve precision. Here's a link to the math...
Large Angle Pendulum Formula

There's a demonstration I do in my math classes to show the sum to product, product to sum trigonometry formulas in action. Beat frequencies and audio interference. You can download free apps that will produce sine waves of given frequencies and phased out of the stereo channels of your mobile device. (Search for "Signal Generator" apps.)

To demonstrate beat frequencies just output two frequencies differing only by a small amount, say 2 Hertz, you will then hear the tone warble at the difference in frequencies.

To do an interference experiment you can then output the two sound channels to a pair of speakers with a specific distance between them (you'll want to do this outside away from any walls or objects that might reflect the sound, say on a card table in the middle of a football field.) Then walk around the them a good distance away and notice in which directions the sound is loudest and in which is least loud. Do this with different frequencies and/or different speaker separation and also with different phase relationships between the two sources if you have an app that lets you control that. This is basically a sound version of the double slit interference experiment.

The math requires the wavelength of the sound which is related to the frequency by the speed of sound. You can thereby use the interference to actually calculate the speed of sound. You might even try comparing the results for different times of day when the air temperature and humidity have changed and see if you can detect a difference.

If you want to get really wild you could combine the beat frequency and interference experiments by outputting slightly different frequencies to the two speakers, you should then observe a moving interference pattern that cycles at the difference in frequency.

Well there are a few I could come up with off the top of my head. I hope they help or at least stimulate your imagination enough to find your own experiments. I don't know your age/school level but I hope I gave enough variety to let you pick a degree of advancement suitable to your level.
Hi! Thank you for your reply, it looks like you put a lot of work into it! I should have mentioned in the original post that the research needs to be original, but your suggestions have certainly stimulated my imagination.

#### berkeman

Mentor
I should have mentioned in the original post that the research needs to be original, but your suggestions have certainly stimulated my imagination.
The research needs to be original? My goodness, what is your level in school? It is pretty hard to do original research unless you are at least in university graduate school and associated with a professor who is overseeing the research.

#### Caesars_son

The research needs to be original? My goodness, what is your level in school? It is pretty hard to do original research unless you are at least in university graduate school and associated with a professor who is overseeing the research.
Sophomore in high school right now.

#### Caesars_son

Sophomore in high school right now.
Most people go down the bio route because its fairly easy to do bio research, but I really want to do work with physics.

#### berkeman

Mentor
Sophomore in high school right now.
Okay, so I guess we need a better definition of the term "original research" in your high school project assignment. Can you post a link to the full assignment, or attach a file that shows the full text of the assignment?

In the general scientific community, "original research" would normally mean new work that has not been published in the peer-reviewed scientific literature. That would put you in the company of mostly PhDs and Masters degree students working with their PhD advisors and supervisors.

Keep on working on learning science -- that is a great thing, and some day you will be doing actual "original research". Or job now is to understand your assignment better, so we can help you to come up with a fun and great project to work on.

#### fresh_42

Mentor
2018 Award
I'm not sure whether this could be called a suitable project by the definition of your school. But my suggestion is a project, one which really often has to be undertaken:

Search a list of reliable sources and references to the topic 'dark matter'.

• This will include papers you probably won't understand, but they usually have an abstract which you might understand.
• It is a good exercise of what will come.
• It should show, that you can distinguish pop science articles or videos from real science. Do not include newspaper or magazine articles in your list. You may include university lectures, videos and seminar papers.
• You could work out a list of conditions which must hold for potential candidates to qualify for dark matter.
• Distinguish between current knowledge and current hypotheses!
In my opinion, this would be an excellent project. It is not lab work, so it may not count, but it is daily business in science.

"In need of help for Physics/Astronomy project"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving