Quiz review - what to expect

1.  Doppler effect
- use of the formula (be sure to understand 't a t a')
- understanding what it means
- red shift, blue shift

2.  Use of trig - Be sure that you can solve for things like:
- sin 20
- finding angle when you know the sine - for example, what is theta when sin(theta) = 0.75

3.  Snell's law and refraction

n = c/v

v = frequency x wavelength

n1 sin (theta 1) = n2 sin (theta 2)

There are two other versions of Snell's law, but you don't actually have to use them - in fact, if you are confused by all the formulas, just forget that those exist and use only the 3 above.

4.  Being able to draw the refracted path when light goes from one medium to another.

SAMPLE PROBLEM:

Light (wavelength 585 nm) goes from air to a new material.  Angle of incidence is 40 degrees and the angle inside the material is 20 degrees.  Both angles are measured with respect to the normal/perpendicular line.  Find the following:

a.  index of refraction of material
b.  speed of light inside material
c.  frequency of light
d.  wavelength of light inside material

HW for Wednesday

Trig practice (if you need/want it):

1.  Find:  

sin 0

sin 30

sin 45

sin 60

sin 90

2.  Find the angle with these sine values:

0.1

0.3

0.75

1

Snell's law

3.  A red light (632 nm = 632 x 10^-9 m) hits a block of glass (n = 1.5) at an angle of 30-degrees (with respect to a normal line).  Draw a picture to represent this, and then find the following:

a.  the angle of refraction inside the glass

b.  the speed of light outside the glass

c.  the speed of light inside the glass

d.  the frequency of light outside/inside the glass

e.  the wavelength of light inside the glass

4.  Draw three parallel lines hitting the side of and refracting these optics:

a.  convex lens (thicker in the middle)

b.  concave lens (thinner in the middle)

5.  Write down anything that still confuses you.

For Monday

Look up definitions of:

Index of refraction

Snell's law

We will do a little trig as well - SOH CAH TOA - have you seen that before?

HW for Thursday

Review your notes from the ripple tank lab. 

Next, find some definitions for:

reflection
refraction
diffraction
interference

Consider these in light of your experiment notes/drawings - how do these definitions match what you saw?  What was happening in your experiment. 

Please write down answers - I will be checking these in our next class.

Doppler problem

An ambulance traveling at 25 m/s has a siren that normally blasts a 1000 Hz tone.  Find the frequency you hear when:

A.  The  ambulance approaches you

B.  the ambulance rives past you

C.  The ambulance approaches you while you run toward it at 5 m/s

D.  The ambulance has past you while you are running away from it at 5 m/s

Doppler Effect!

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

http://falstad.com/mathphysics.html

Run the Ripple tank applet -

http://falstad.com/ripple/

The key in the Doppler effect is that motion makes the "detected" or "perceived" frequencies higher or lower.

If the source is moving toward you, you detect/measure a higher frequency - this is called a BLUE SHIFT.

If the source is moving away from you, you detect/measure a lower frequency - this is called a RED SHIFT. Distant galaxies in the universe are moving away from us, as determined by their red shifts. This indicates that the universe is indeed expanding (first shown by E. Hubble). The 2011 Nobel Prize in Physics went to local physicist Adam Riess (and 2 others) for the discovery of the accelerating expansion of the universe. Awesome stuff!

http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/

It's worth noting that the effect also works in reverse. If you (the detector) move toward a sound-emitter, you'll detect a higher frequency. If you move away from a detector move away from a sound-emitter, you'll detect a lower frequency.

Mind you, these Doppler effects only happen WHILE there is relative motion between source and detector (you).

And they also work for light. In fact, the terms red shift and blue shift refer mainly to light (or other electromagnetic) phenomena.

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More music-related sites, FYI:

http://www.youtube.com/watch?v=XKRj-T4l-e8

http://www.youtube.com/watch?v=cPALfz-6pnQ

https://www.youtube.com/watch?v=aWAjLOwOHU0

http://www.acs.psu.edu/drussell/Demos/TuningFork/fork-modes.html

HW for Friday

Read up about the Doppler effect for our next class.  Take notes.