Optional HW for practice

Happy Thanksgiving!  Here's some physics for you to play with.  I will post the answers as a "comment" below, a little later.

1.  Consider this right triangle:  36, 77, 85

Draw this and find the angles in the triangle.

2.  Repeat for this triangle:  20, 21, 29

3.  What is the index of refraction for a material that slows light to 3/4 of its vacuum speed?

4.  Lights goes from air (n = 1) to a new material, being refracted from 75 degrees to 38 degrees.  Find the index of refraction of the new material.  (Angles are measured, as always, with respect to the normal line.)

Homework - do as many as you can.

Here's some fun stuff to do over the weekend!

Trig stuff

1.  Consider a right triangle with sides:  5, 12, 13.

a.  Draw this
b.  Find the ratios for sin, cos and tan.  (Remember SOH CAH TOA.)
c.  Use the inverse functions (sin^-1) to find the angles.  You can also use the fact that the angles of a triangle add to 180 degrees, if that is helpful.

2.  Repeat the above exercise, if helpful, for another pythagorean of your choice.  See:

http://en.wikipedia.org/wiki/Pythagorean_triple

3.  Use your calculator to find:

a.  sin 30
b.  sin 0
c.  sin 90
d.  cos 0
e.  cos 90
f.  tan 45

Index of refraction

4.  Describe WHY refraction occurs.

5.  Review the definition of index of refraction.  Review, if helpful:

http://www.physics.uoguelph.ca/applets/Intro_physics/refraction/LightRefract.html

6.  Find the index of refraction of a substance in which the speed of light goes to HALF its value in a vacuum.  (Recall that c = 3 x 10^8 m/s.)

7.  The speed of light in a piece of plastic is 2.5 x 10^8 m/s.  What is its index of refraction?

Snell's Law

8.  Light passes from air (n = 1) to a block of new stuff, with the angle going from 60 degrees outside the block to 35 degrees inside the block.  The angles are measured with respect to a normal (perpendicular) line.

a.  Draw this.
b.  Calculate the index of refraction of the stuff.

Refraction homework

1.  Find a definition for "index of refraction." 

2.  Look up "Snell's Law".  It will likely have a "sin" of an angle in the equation.  See how much of this makes sense to you.  If you find an equation for it, make sure you have a picture that goes with it.

3.  Play around with this applet (from class):

http://www.physics.uoguelph.ca/applets/Intro_physics/refraction/LightRefract.html

4.  You have a sense of what happens when light goes from air (or a vacuum) into water (or plastic, glass, etc.).  What do you suppose happens when light goes from water into air?  Draw this out and explain.

HW for Tuesday

1.  Come up with a definition of (wave) reflection.

2.  Come up with a definition of (wave) refraction.

You can look online, but make sure that the topics are clear to you (and written in your own voice).  USE PICTURES, too.

hw

http://www.darvill.clara.net/emag/index.htm

Visit this page and read about the various types of electromagnetic radiation.

And if you have more time:

http://en.wikipedia.org/wiki/Electromagnetic_spectrum



Also, bring test-related questions on Wednesday.

Electromagnetic Spectrum Images

For next class

Read up on the Doppler effect.  Play with the applets, if you wish:

http://falstad.com/ripple/

http://www.lon-capa.org/~mmp/applist/doppler/d.htm

And - some practice problems to try before the test (which will be the week after the upcoming short week.)

1.  B is 466.1 Hz, approximately.  Find the following frequencies:

a.  the next 2 octaves
b.  the 2 octaves below
c.  the C above (one semi-tone)
d.  the D above (3 semi-tones)

2.  Be able to conceptually/physically explain the Doppler effect.

3.  Consider a tube open on both ends, 0.4-m in length.  Find the relevant stuff for the first 3 harmonics:  wavelengths, frequencies, shapes.  How would answers change for the same tube capped on one end?

4.  Review the recent quiz and make sure you understand the string/harmonics stuff.

5.  Review the speed of sound lab in your notes.

Remember:  Proper prior preparation prevents poor performance.