I wonder what would their world look like if they knew that light can be bent. Well, in huge distances (like space) light is bent with gravit, which is pretty cool, but it takes a big body of mass and quite a large distance to do that. I am not going to travel light years to see light bend. I’m going to do it in my own bathroom. You can too. In your own bathroom.

So what actually happens with light to cause it to “bend”? In short distances, light travels in straight lines, and if they are otherwise undisturbed, they will go on forever. Or at least for a really really really really long time. That’s how we see distant stars, their light travels huge distances and reaches our telescopes (or eyes, if the night is clear).

Using the principle of refraction, we can simulate a situation where a light beam is ‘bent’. Think about a bunch of mirrors, each refracting the light in a slight angle towards another mirror – eventually directing a beam of light at a completely different angle. That seems easy enough, and – unsurprisingly – that is exactly what is happening within the flow of water.

Materials for the Experiment

• A Plastic Bottle – preferably clear and empty.
• Duct Tape. (I used blue, you can use whichever color you feel like).
• Laser Pen, or other directed light source.
• Water.

Preparations

Take the plastic bottle and poke a hole in it with a pin. I recommend expanding it a bit, the hole in my bottle was about 2mm in radius. The trick is to create a large enough hole to encompase the entire laser beam, but not large enough to have the water just pour out uncontrollably. It took me about 3 attempts to get this straight. Err.. bent.

Now, cover the hole with the duct tape and poke another hole through the not-for-long sealed hole. The duct tape is not absolutely necessary, but it will help directing the laser ray towards the hole. You would be amazed how difficult it can be to aim when water is pouring out on top of you…

Seal the hole with your finger and fill the bottle with water. When it’s full, close the cap. The pressure inside the bottle will prevent the water from coming out through the hole – as long as you are careful not to squeeze the bottle. Or drop it. Or tilt it too fast…. okay, maybe you should keep your finger on the hole anyway.

Put the bottle somewhere wet (or that you wouldn’t mind getting wet, like a bath tub), turn your laser beam on and point it at the hole. Release the cap.

Water should be coming out now, and if you aim your laser light properly, they should refract the beam towards the surface and appear slightly reddish (or.. whatever color your laser beam is).

Real Life Applications

• Optic Cables: Spread over the ocean and land, optic cables direct light from one point to another using this principle. No, they are not made of water, they’re made of a matterial that is, actually, better refracting (light beams don’t ‘come out’ of the cable mid-way, usually, only at its ends). This means that the light does not lose energy along the way, and reaches the destination in the speed of light. Which is fast. Very fast. Yay for optic cables.

Resources

• Light Refraction: http://www.ps.missouri.edu/rickspage/refract/refraction.html
• Refraction of Light: http://sol.sci.uop.edu/~jfalward/refraction/refraction.html
• Full Bottle, Hole, No Leak: http://www.newton.dep.anl.gov/askasci/phy00/phy00946.htm
• howtoons: http://www.instructables.com/id/Bending-Light/

Of course, it only takes a few years and a drivers license to understand that a car that actually sounds like that while standing is not quite the car you would like to buy. Or rent. Or.. get into.

So why are we all using this sound to describe the moving car? What happens to the sound of a car when it is moving to get it to change so dramatically? I wonder.

No more.

No more wondering, that is. Cars will stick around. At least for a bit, until we start with the hovercrafts… and everyone knows they go “fffffffffffffffffffffzzzzzzzhhuuuuuum!” anyways.

The next experiment explains the phenomena called “The Doppler Effect“, where waves (not just sound waves, mind you. Doppler welcomes waves of all kinds, shapes and frequencies), seem different in movement.

A ‘Wavy’ Reminder:

Just so we’re all in the same level, here’s a reminder: We can describe waves with a few main characteristics: Amplitude, Wavelength and Frequency.

• Amplitude defines the “strength” of the wave. In sound waves, it is the factor that determines how loud the sound is.
• Wavelength is one full cycle the wave ‘completes’ from 0 to 180 (or, from ‘peak to peak’).
• Frequency is determined by the amount of cycles (wavelengths) per second.Hight frequency will result in many cycles per second, and therefore a very small wavelength. Low frequency means few cycles per second and a long wavelength.

Formula for the Doppler Effect:

f is the original frequency in movement, and f’ is the “resulting” frequency (the one the mommy duckie actually hears).

V is the speed of the wave itself. Sound waves in air, for instance, have a speed of approximately 330 meters per second.

Vs is the speed of the moving object that is creating the sound – for that matter, the speed of my duckie. Solving that equation gives the resulting frequency (the “pitch”) that the stationary listener receives.

Preparations:

I didn’t have a lot of time to prepare, and I didn’t want to spend too much money on materials, so instead of working on properly connecting the buzzer to a battery, I just hooked up something very.. uhm.. amateurish. Anticipating the comments some of you will probably post, I must state, in advance, that I know it’s amateurish. I just don’t care. It worked.

Here’s the buzzer before:

I bought it for $1.60 in one of the main electronics shops (you could probably find it for a lot cheaper in a non-franchise (or just outside of Manhattan).

For whoever’s interested, the original (non moving!) specified frequency for it is 2700+- 500Hz.

After I tweaked with it a bit and used paper clips (because that’s what I have here), it took the shape of this lovely piece of art (though an incredibly annoying one):

That unconnected red line – when connected to the batteries – closes the circuit and activates the buzzer. I had to unhook it for fear of my sanity. Handle with care.

You can purchase an already-built buzzer. I am just too cheap.

Also, a friend of mine gave me the idea of playing a continuous single-note mp3 file (if you can find, or record one) on your favourite mp3 player and fling around the earphones. (Nice idea, genius, next time you spend 10 minutes building a stupid buzzer.)

Materials Used in this Experiment:

• 2 Rubber Duckies with their Rubber Duckie Mommy.
• Any kind of bucket, tub or bowl. Preferably clean water.
• A buzzer or any type of annoying sound making device ($1.60 in Radio Shack). Do not use a baby.
• Batteries for your buzzer (or whatever else makes it go bzzzz).
• A Tennis ball.
• A stocking (don’t take a nice one, the owner of that stocking will not like it).
• A trusted (and trusting) friend.

So, What do you do? Simple. You turn the buzzer on, shove it into the tennis ball so that whatever happens it doesn’t break (and, also, if your hand gets slippery and it whooshes off to space, your friend’s face will have a nice round bump instead of a nasty battery-shaped one). You shove the now-very-annoying tennis ball into the stocking –

Note: This is the time to call your friend over to enjoy the wonders of this phenomenon. You, as the buzzer-slingshot performer, wont really notice any sound changes, but the person in front of you will, and your friend will thank you from the bottom of his heart.

Or his ear. Whichever will hurt less.

– start twirling the stocking around like a lasso above your head, or next to your body.

The buzzer moves quickly closer and farther from the person in front of you and the Doppler Effect kicks in. It might not sound as cool as a car ‘zhoooooooom’ing by but it certainly proves the point. Stop twirling the buzzer around and show your (hopefully appreciative) friend that the buzzer has a constant sound when it’s not brutally slingshot through the air.

Voila. You’ve created the Doppler Effect in your own house. Aren’t you proud?

Practical Applications

The Doppler Effect, as I stated before, does not discriminate on the type of waves it operates on. For that reason it has a lot of practical applications:

• Police Radar: Yup! When police officers measure the speed of a passing car using their nifty-looking radar-gadget, that’s how they’re doing it. Well, they’re not actually calculating it themselves, of course, the radar is doing it for them – but it is using the Doppler Effect. The device is sending a wave with constant frequency towards a passing car and expects the reflection. Since the car is in movement, the reflection is bound to come back distorted from the Doppler Effect. Using the formula, it then calculates the exact speed of the passing car and notifies the police officer if a ticket is needed.
• “Red Shift”: As we said, the Doppler Effect acts on waves of all kinds, including light. With light the effect is emphasized because different frequencies of light waves mean different visible colors. When astronomers look at the sky in search of new (and existing) galaxies, they measure the light frequencies from that galaxy. Galaxies that are shifted towards the “red” spectrum are lower frequency, and galaxies that are shifted to the “blue” spectrum are higher frequency. “Red Shift” is the term used on galaxies that move away from Earth, where their visible and invisible light frequencies are lower – shifted to the ‘red spectrum’. Measuring exact shifts can help astronomers understand how fast a stellar object is moving away (or towards) us.
• Airplanes: Since airplanes are moving, the ground always receives a distorted transmission. For that reason, airplanes never use frequency-modulations (FM) for their transmissions (even though FM transmission is considered to be of higher quality) but rather modulations that are based on amplitude (AM). That way the ground can decipher the messages quickly regardless of the distortion and changes in speed.
• Breaking the Sound Barrier:Moving airplanes get really fast. Really really fast, actually. If a plane moves faster than the spread of the sound waves, it is considered to “break” the sound barrier. A nice representation of it can be seen in this link from Kettering University.

Resources:

• http://www.seed.slb.com/en/scictr/lab/doppler/index.htm
• http://www.fearofphysics.com/cgi-bin/doppler.cgi?dir=a&vs=300&mode=wrap
• Doppler Effect and Red Shift: http://www.youtube.com/watch?v=Man9ulEYSgk
• http://www.space.com/scienceastronomy/redshift.html

Note: If you have been to this post before, you might’ve missed quite a big error that was spread around through the text. Accidentally, I wrote 300*10^8m/s instead of 3.0*10^8m/s which is quite a large difference (and is absolutely wrong, too!). I apologize for the mistake, and hope that if you came back, at least I can correct it so that readers will have the correct number. The speed of light is 3.0 * 10^8 m/s – or 300,000,000 m/s. Thanks to Gonelli for the sharp attention

Of course, any educated deer knows that light moves at approximately 3.0*10^8 meters per second, which is very fast. It is wise, therefore, to move away very fast. But, as luck goes, by the time that realization passes the deer’s mind… well, you know. Poor deer.

But, that’s life. It’s not the only disturbing thing that may happen with speedy objects rushing through the air. It once struck me that I had no idea how baseball announcers knew the exact speed of a flying fastball.How about the speed of a baseball that’s just been hit out of the park?How fast is it traveling when it hits that car window in the parking lot?It’s moving so fast you couldn’t possibly measure its speed without fancy instruments.So, if its so hard to measure a baseball’s speed, how in the world can we measure the speed of light?

How can scientists be so sure of its speed with such certainty?And why should we believe them?

So.. no more! You don’t have to take their word for it. From now on, you can measure it for yourself with this – pretty nifty – home experiment.

Materials Used in this Experiment:

• Long chocolate bar – $2.00, $3.50 in NYC
• Microwave Oven: $100
• Plate: Clean, preferably. (Microwave safe if you like your microwave)
• Calculator: Not a must (but see the section titled Time for experiment)
• Ruler: $0.11 if you buy by the thousands.
• Personal, intimate knowledge of the speed of light: Priceless

Time for experiment:

About 10 minutes (with a calculator.15 without one. Could be a lot more if you forgot your fifth grade math).

Accuracy:

There will be some inaccuracy in your result (my own calculations had a percent error of 6.3%). The size of this error is important, because it can help us understand what external factors played a role in our experiment.If you stop to consider your results, why you got them, and what they mean, it’ll help you understand how light works.

Since this experiment is done at home (which is not conducive to precise measurements, unless you live in a physics lab, in which case I am willing to relocate for a domestic partnership) there are several external conditions that could distort the measurements and lead to errors.This is by no means a complete list, but here are some external factors that I thought of:

• Uncertainty about the exact position of the plate inside the microwave oven. I had no way of knowing how high, or low, to put the chocolate inside the microwave so the waves would hit said chocolate at the x-axis and produce a relatively useful waveform on the chocolate. However, the microwave is relatively small, and I tried to align the plate with the wave generator (or what looked like one).
• There is air in the microwave oven. This type of experiments is best done in a vacuum, to eliminate any interference from “external” sources like resistance, humidity, etc. The electromagnetic (light) waves themselves might not be affected, but the chocolate certainly is.
• My measurement was relatively generous, on the broad side. If the chocolate had melted at two distinct points, I could have taken a more accurate reading. On top of that, my measuring devices – a ruler and two imperfect eyes – were of limited accuracy.Real labs with real scientists have very accurate measuring devices which decrease the percent error.

To try and eliminate such mistakes from affecting real experiments, real scientists never stop after only one experiment. The tests are repeated over and over again, and sometimes even over again, again, and all results(failures and successesses(whatever)) are recorded and analyzed. My experiment was only a demonstration, but if I’d have done it a few more times, and taken an average of the distance between entry/exit points of the wave, my accuracy level would probably rise.

Despite all this, I have to say: measuring the speed of light in non-lab conditions, using a bunch of Hershey’s Kisses and a plastic ruler, and getting only a 6.3% percent error, well, that ain’t too shabby.

Practical Applications:

There are many applications to knowing the speed of light, and mentioning all of them would be a crazy, crazy task even for me. However, for the sake of consistency, here are a few interesting scientific applications that use the speed of light:

• GPS Systems can pinpoint signal location on earth with calculations based on the speed of light.The GPS device (in your hand, for instance) receives a locator beam from multiple satellites at various locations in orbit. At any given time, GPS satellites are located over different parts of the Earth, and they all send out a signal synchronized to each other according to an atomic clock.In other words, they all broadcast at exactly the same time.But because the satellites are at different distances from you, your GPS unit will receive these synchronous signals at different times.Why?Because the signals, despite being broadcast at the same moment and traveling at the same speed (of light!) arrive at your location in a staggered manner – sooner from closer satellites, later for farther ones.Calculating the relative delays of the signals lets your GPS unit figure out where you are to an exceptional degree of accuracy.
• Communication in Space: The speed of light affects communication in general (since light itself, as we said, is an electromagnetic wave, just like radio waves but at a different frequency) but the most noticeable effect is on communication in space. When Houston ground control (as in, “Houston.. we have a problem!”) communicated with Apollo 8, the first Apollo mission to orbit the moon, they had to wait about 3 seconds until their messages reached the astronauts.
• Distances in Space: Because distances in space are so vast and the speed of light is constant in a vacuum and thus the same number always, distances to far solar systems, planets and other stellar objects are often referred to in “light years.” In colonel general, the units of “parsec” (“parallax second”) and kilometers are used, but to convey the sheer size of those distances, they are expressed in terms of the speed of light.
  This method of measurement is defined as the distance a light beam travels in a certain amount of time. For example, expressing the distance to Alpha Centauri system as 4.3 light years (meaning light from there takes 4.3 years to reach the Earth) is much more comfortable than trying to say, write, type or remember it as a distance of 4.06802721 * 10^13 km.

Isn’t light brilliant?- I know, I didn’t laugh either.

Remember: True science is about experimentation and observation. If you use your brain to do some thinking, the world is at your feet!(Of course the world is at your feet anyway, but if you don’t think you won’t know what to do with it.)

(lots of thanks to Daniel, who helped me out with English, jokes, and a decent way of combining the two.)

Resources:

Speed of light:

• http://en.wikipedia.org/wiki/Speed_of…
• http://www.colorado.edu/physics/2000/…
• http://math.ucr.edu/home/baez/physics…
• http://galileoandeinstein.physics.vir…

Electromagnetic Waves:

• http://science.hq.nasa.gov/kids/image…
• http://www.colorado.edu/physics/2000/…

Original idea (You can also find more information of how to conduct this experiment yourselves):

• http://www.null-hypothesis.co.uk/scie…

Similar Experiment:

• http://www.physics.umd.edu/icpe/newsletters/n34/marshmal.htm