text of the lab

Waves in a Ripple Tank - a semi-formal group lab

This is a bit of a strange lab.  First, it is a group lab - to be submitted by the group as one document.  You will witness waves in a different fashion than we have in the last several classes:  waves in water.  This is useful, as light (our next topic) behaves in a wave-like fashion under several circumstances.

For this lab, I would like you to begin by writing your own personal definitions of these words: 

Reflection, refraction, diffraction, interference

This will serve as a hypothesis.  How do you expect to see these phenomena represented in water?  This is a largely visual, non-quantitative lab.  Enjoy!

For your "data", draw everything you see and make relevant comments.  Each lab partner should do this in his or her lab notebook.

1.  Propagation of waves

Dip your finger in the water repeatedly, with constant frequency.  Comment.  We will call these "circular waves" in this lab.

Do the same with a ruler, commenting on what is seen.  We will call these "straight waves" in this lab.

2.  Reflection of waves

Send a wave (or waves) into a barrier.  Try this directly (no angle) at first, and then at some angle.  Discuss.

3.  Refraction of waves

This can be tricky to see, but there is something to be observed.  Set up an area with deep water and shallow water (using a piece of Plexiglas) to see what happens when water passes from one medium (deep) to another (shallow), or vice versa.  Try this directly and also at an angle (as above).

4.  Diffraction of waves

Send straight waves to a barrier as shown.

Now send them through a small opening, changing the size of the opening and noting the effects.  Comment on all scenarios.

5.  Interference of waves

This can also be tough to see.  Instead of creating one set of circular waves, create 2 sets (with 2 fingers) at the same frequency.  Watch what happens when they "interact" with each other.  Comment and draw if at all possible

Some of these things can be tough to see.  You may want to play with the applet below to see what would be seen under ideal circumstances for some of these cases.

http://falstad.com/ripple/

In your group's conclusion, comment on what you saw, especially as it relates to what you thought you'd see.  Give updated definitions of the words initially mentioned in the lab introduction.