Unrelated, but fairly awesome.

http://gizmodo.com/5850643/what-the-hell-magnets-why-are-you-so-amazing?tag=science

http://andrewsullivan.thedailybeast.com/2011/11/ment-5.html

homework: C and E

Apologies to C-block for not posting this sooner. E-block, this is for Friday's class.

Before next class, find the definitions of:

focal point (or focal length)

thin lens (or mirror) equation - show the equation and tell what the variables represent.

Thanks very much. If you do not get to it, because you expected it last night, I understand.

In the lab, we will take this approach:

1. Set up optical bench, using a convex lens first. Your "object" will be a candle. Find a theoretical focal length, using the method discussed in class.

2. Vary the object distance (do) and note how the resulting images (if there are images) change.

3. Watch for these things, and make notes (in a table). Is the image:

a. bigger, smaller or same size as object

b. right-side up or upside down

c. real or virtual

d. where is the image located (di)?

4. You will repeat this for a concave lens, concave mirror and convex mirror.

5. In general, you will be seeking to determine how lenses and mirrors form images, when they form images and how they form images.

6. The lens/mirror equation is very good for making predictions as to how images are formed (and what types of images are formed). You will use the lens equation to calculate an experimental focal length and compare it to your theoretical focal length (with percent error).

7. Other lab questions will be posted.

Prep for Next Formal Lab homework

In our next formal lab, we will investigate how images form. Find out the meaning of these terms:

real image
virtual image
convex lens
concave lens
convex mirror
concave mirror
plane mirror

This is homework mainly for C block class, but E block class should do it if they have time (after the 5 critical angle problems).

Applet fun

http://stwww.weizmann.ac.il/Lasers/laserweb/Java/Twoangles2.htm

http://groups.physics.northwestern.edu/vpl/optics/snell.html

homework (C and E)

Review the material on:

Critical angle
Total internal reflection
Snell's law and how to get angles using the 2nd SIN function (inverse sine) on your calculator.

Also, answer these questions:

1. Calculate the critical angle for water (n = 1.33).

2. Determine the index of refraction of a substance with critical angle 50 degrees.

3. If you were trying to hit a fish with a spear (like in the movie, "Castaway"), should you aim above, below or at the fish in the water?

4. If you were trying to hit the fish in the previous problem with a laser, would your answer change? How so?

5. If the cosine of an angle is 0.4, what is the value of that angle?

Homework (E) - same as C below

Homework (C)
Have a go at these problems:

1. What is the index of refraction of a substance that reduces the speed of light to 75% of its value in a vacuum?

2. What is the speed of light in water (n = 1.33)?

3. A light ray enters a piece of plastic at an angle of 60 degrees (with respect to the normal line). It is refracted to an angle of 40 degrees. What is the index of refraction of the plastic? Assume that the index of refraction of air is 1.

4. Can an index of refraction be less than one?

5. What are the units of index of refraction?

6*. A light ray hits a piece of quartz (index of refraction = 1.46) at an angle of 30 degrees (with respect to normal). What is the angle of refraction inside the quartz? (Hint: Solve for the sine of the angle, and then take the 'inverse sine' on your calculator. That would be the 2nd SIN key.)

7. What is atmospheric refraction?

8*. How do prisms break up white light into colors?

* tricky

Refraction applets, FYI

http://www.launc.tased.edu.au/online/sciences/physics/refrac.html

http://www.lon-capa.org/~mmp/kap25/Snell/app.htm

http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/Physics/refractionsnells.htm
(But note that the wave goes into a LESS dense medium, thus refracting AWAY from normal line.)

Enjoy!

Homework (C)

Have a go at these problems:

1. What is the index of refraction of a substance that reduces the speed of light to 75% of its value in a vacuum?

2. What is the speed of light in water (n = 1.33)?

3. A light ray enters a piece of plastic at an angle of 60 degrees (with respect to the normal line). It is refracted to an angle of 40 degrees. What is the index of refraction of the plastic? Assume that the index of refraction of air is 1.

4. Can an index of refraction be less than one?

5. What are the units of index of refraction?

6*. A light ray hits a piece of quartz (index of refraction = 1.46) at an angle of 30 degrees (with respect to normal). What is the angle of refraction inside the quartz? (Hint: Solve for the sine of the angle, and then take the 'inverse sine' on your calculator. That would be the 2nd SIN key.)

7. What is atmospheric refraction?

8*. How do prisms break up white light into colors?

* tricky

Homework E block

Investigate and write meaningful definitions for these concepts -

Index of refraction

Snell's law

homework (C)

Find the meaning/definition of the following:

Snell's law

Index of refraction

Also, examine your data/graphs - particularly the graph of sin (theta 2) vs. sin (theta 1). Does it make sense in light of Snell's law?

homework

C block - none! (You just finished the test.)

E block - study for test.

review board

Electromagnetic Spectrum

Recall that waves can be categorized into two major divisions:

Mechanical waves, which require a medium. These include sound, water and waves on a (guitar, etc.) string

Electromagnetic waves, which travel best where there is NO medium (vacuum), though they can typically travel through a medium as well. All electromagnetic waves can be represented on a chart, usually going from low frequency (radio waves) to high frequency (gamma rays). This translates to: long wavelength to short wavelength.

All of these EM waves travel at the same speed in a vacuum: the speed of light (c). Thus, the standard wave velocity equation becomes:

c = f l

where c is the speed of light (3 x 10^8 m/s), f is frequency (in Hz) and l (which should be lambda) is wavelength (in m).

HW

For C block - Go through your notes and generate a review page.

For E block - that will be your homework after Thursday's class. For tomorrow, make sure you did the Doppler problem creation already assigned.

Thanks!

Hw

Oops

I posted the homework (for E block) on the wrong blog - homework is to create and solve your own Doppler effect problem, with at least 4 parts.

This is the same hw as is due Wednesday for C block.

Thanks!