The Physics Blog

Standing Wave on String. Videos to Watch.

The animation is from the Wikipedia pages on Standing Waves

This first video shows how two sine waves moving in opposite directions add to give a standing wave form. You might want to pause it and look at what the curves are doing from one moment to the next. Watch it a couple of times.

 Bad music but it looks really good.

This next video shows what those standing waves look like on a string.

And this is a video (Chinese Language) of a standing wave on a spring.

Wave Interference and that Triangle to Find Wavelength

This is the YouTube we watched with the two sources of circular waves producing constructive and destructive interference patterns.

I found this Power Point on the University of Glasgow Physics Department pages (thank you to them) I cut it down to 4 slides that give us nicely what we need to have.

You need to be able to draw the diagram, show what all of the side lengths are and use the equation you develop for the Sin (A) to find the wavelength of light.

Here it is.

Download Young's Experiment 

Harmonics and Resonant Modes of Vibration

This is a very good link to the University of New South Wales in Australia's website on Acoustics. I think it is even better than Kettering's pages for the detail and clarity on harmonics.

Y12 Traveling Wave Questions

Here is the sheet I gave out in class last week.

You will need to give justifications and qualitative answers to the first four questions and then the calculations that follow require you to use the equation speed = frequency x wavelength.

Download TravellingwaveHWK 

Don't forget to use UNITS in your answers and to use STANDARD FORM.

Resonance

This is the video of the Tocoma Narrows Bridge that we talked about in class.

Simple Harmonic Motion

Here is the sheet that I gave out in class

Download SHM Questions 

And here are the solutions

Download SHM Solution 

If you want to read more about SHM and the way that we can use and apply it then look at HYPERPHYSICS and follow the links to Mechanics and then Periodic Motion.

Spring Constant and Period of Oscillation

You should have two sets of data now; one for the extension of your spring as you add mass to it and one for the period of the oscillation of the mass on the spring as you change ONE variable.

You need to plot these data on two separate graphs and use the graphs to try and find the relationships you are looking for.

Remember what to look for on the graphs:

Lines of best fit, not necessarily STRAIGHT. DO NOT JOIN THE DOTS.

Draw AXES with units on the graph. Put the lines of the axes on the graph and write the units like this....

Period / s       NOT        Period (s)

Always find the GRADIENT of a straight line. What does it mean? What are its UNITS?

What is special about a straight line through the origin?

How do you find the relationship if you have a curved line? What is it likely to be? If you could somehow turn the curve into a straight line then you might get somewhere..... What could you try doing to one of the variables that you plot that might give you a straight line?

The Electromagnetic Spectrum

Here are links to two interesting versions of the Electromagnetic Spectrum for you to view at your leisure.

This one is entertaining, reasonably accurate and full of detail but there are some things on it that are confusing, like the mention of sound waves!

This one is more scientifically accurate but less entertaining.

Graphing our 'Waves'

So we looked at the general equation for a waveform

y = A Sin (Bx - Ct)

And saw what effect changing the variables A, B and C had on the shape, position and nature of the wave form. Carla pointed out that we could also do y = A Sin (Bx - Ct)+1; what effect would that have?

If you want a good online Graphing Calculator to play with and go over our curves then follow the link.

The Curves we did in class were

y = Sin(x)

y = 2Sin(x)

y = Sin(2x)

y = Sin(x-1)

Reflection and Refraction Results

Reflection and Refraction Experiment

What you need to do with the results is look up Snell's law in a book and see if they can be used to verify the law. Now that is all quite straight forward, what would be really impressive is for you to do what Snell did and actually PREDICT the law. There is a way of doing it graphically by using Huygan's Principle. The key is to remember what causes refraction, it is the change in speed of light whan it travels from one medium to another of different (optical) density.