Waves in 2D Test

Waves in 2D Review

Waves in Two Dimensions Review

Today in class we went over questions 16 and 17 in the green booklet on Waves in two dimensions. We also corrected the answers on the review sheets so we can prepare for the test on Wednesday.
Scribe for Thursday is kristina

Wednesday Sept 26 (i know im kinda late sorry)

On Wednesday we had a substitute and his name was Mr. Whiteway (he was a English teacher so he wasn't much help). We received 2 handouts on Refraction. One was about how light refracted and the other was exercises on Refraction.

Friday September 29

Hi, I'm Thi and I'll be scribing for Friday's Class. On Friday, we watched a video disk on interference of two circular waves and Diffraction. Note: I put diffraction in bold and Italics because it may be on a test. Diffraction occurs when a wave, for example, made in a ripple tank hits an obstacle. Although the wave may reflect, it will also pass through the barrier at its ends. This causes the wave to slightly bend and is known as diffraction. Diffraction can change a straight wave into almost a circular wave.

When two identical waves that are produced by two point sources collide, they interference with one another. This results in crests overlapping crests, troughs on troughs and even crests on troughs. Areas of destructive interference and constructive interference are created. As shown in the Waves in Two Dimensions booklet and the assignment we received, dotted lines are correspondent with the troughs, solid lines with crests and the grey area is the path of the nodal lines.

Page 17 of the booklet displays what this looks like and explains everything I just said and more.Click to see Page 17

After that we received a worksheet on interference and that is basically all I can remember of Friday's Class.


Since I am the last one to scribe, I guess I have the honour of choosing the next scribe. The next scribe shall be Kevin! For future references, I stink at blogging and this is goodbye for now.

Hey this is Eric, and I'm today's scribe.

Today in class we watched a video of a crazy teacher who explained waves in two dimensions: reflection and refraction. We also got a worksheet to fill out while we watched the video.

After that, we looked over the answers, which everyone should have since we did them in class.

We then went over the answers for last week's homework, which was:
Questions 5 to 8 in the green booklet

Answers:

Finally, we got an assignment on Refraction that doesn't have to be done for tomorrow, but it would be good if you did some. Also, don't forget to do your research projects!

That's all for today, and the next scribe is Melissa since the scribe today was actually supposed to be her

Hello. This is lauressa.

Well today in class we went over page 12 in our green booklet; waves in two dimensions, and learned about Snell's Law. Snell's Law shows that the ratio of the sine of the angle of incidence and the sine of the angle of refraction is a constant. The constant we use in Snell's Law is referred to as the index of refraction. With Snell's Law it can be used to determine a number of things, for instance the speeds and the wavelengths of incident or refracted waves by this equation

For those who aren't quite sure what refraction is it occurs when waves approach a boundary between two water depths at an angle causing the direction of travel of the refracted waves change. Since the value of n are ratio it doesn't have any specific unit of measurement, but the value of n, is specific for certain materials like air, glass, and water. For Snell's Law we also used old equations but with a little twist. As we all know velocity V, can be found by multiplying frequency F x wavelength λ. Well we can use that equation for help with Snell's Law by putting deep .vs. shallow in front the the characters to solve for the velocity of the deep and shallow water.

After we learned about Snell's law Ms.K handed out an assignment to test how much we could put our knowledge to use. Here was the example questions and the answers if you didn't manage to get them in class.

A water wave of frequency 10.0Hz and speed 40cm/s is traveling in deep water. It then moves into shallow water where its speed is 30cm/s. The angle of refraction is 30°

Find
A) The index of refraction
n=Vdeep /V shallow

n=(40cm/s)/(30cm/s)

n=1.33

B) The wavelengths in the two media

Deep
λdeep=Vdeep/F

=(40cm/s)/10.0Hz

λdeep=4cm

Shallow
λshallow=Vshallow/F

=(30cm/s)/10.0Hz

λshallow=3cm

C)the angle of refraction in the shallow water.
For this question there is more than one way to solve it .

~solution 1~
n=sinθi/sinθr

sinθr=sin30°/1.33

sinθr=0.375 or 22°


~solution 2~
sinθi/sinθr=Vi/Vr

sinθr=(sinθi x Vr)/Vi

=(sin30° x 30cm/s)/(40cm/s)

sinθr=0.375 or 22°


~solution 3~
sinθi/sinθr=λdeep/λshallow

sinθr=(sinθi x λshallow)/λdeep

=(sin30° x 3 cm)/4cm

sinθr=0.375 or 22°

Well that was pretty much it for our class on Friday, but for those who haven't already, the assignment for the week were questions 5-8 in our green booklet, and our wave research project is due on Tuesday. See you all on Monday!!
O yea the next scribe is Melissa

If you're thinking you should realize that question #6 is a repeat of the question we did on the whiteboard.

Waves Moving From One Depth to Another & Refractions

Hello! This is Mary Ann.

In class today, we got our assignments and test back. We went over the answers for the test, so if you missed any of them..here they are!

1.


This is a transverse wave.


2. amplitude = 1.5 cm
wavelength = 4.5 cm


3. a. longitudinal
b. (i) compression
(ii) rarefaction
(iii) wavelength


4. a. f = 50/10 = 5Hz
b. T = 1/5 = 0.2s


5.
The wave should appear inverted since it hits a fixed end.

6. This is how your diagrams should have turned out.

7.


8.

9. Constructive Interference: occurs when two pulses on the same side pass through each other. This causes the amplitude to increase.
Destructive Interference: occurs when two pulses on opposite sides cancel when overlapped.

10. The main function of a wave is to transfer energy through a medium.

11. a) true
b) meters or cm
c) true
d) normal
e) transverse

12. A standing wave consists of two waves of equal amplitude, frequency and wavelength.

The red dots represent the nodes. The blue dots represent the anti nodes.

After making corrections on the test, we looked into the green booklet on page 9-11 and learned about Waves Moving From One Depth to Another & REFRACTIONS.

When waves move from one depth to another, the frequency does not change. What changes is the speed of the waves. In deep water, the speed of the waves is vdeep = (fdeep)(λdeep). The speed of the waves in shallow water is vshallow = (fshallow)(λshallow). Since the two frequencies are the same it can also be written as vdeep/vshallow = λdeep/λshallow.

In this picture it shows a straw in a glass of water that appears to be broken but it is actually being refracted since half of it is in water and the other in air. Air and water are the two mediums in this case.

*NOTE*
-The 5 questions on Waves in Two Dimensions - Assignment 1 is due tomorrow.
-Our project is due on Tuesday, September 25th.

The next scribe is going to be LAURESSA.

Straight Barrier: Wavefront

Hello everyone, this is Lina with today's scribe post.


We started today's class by going over the worksheet we recieved yesterday about wavefronts and wave rays. It was pretty straight forward.


Here are a couple of definitions for you:

A wavefront is a continuous crest or trough.
A wave ray is to show the direction of travel/transmission of the wavefront.
Remember: The wave ray is always perpendicular to the wavefront. You can also say that the wave ray is at a right angle to the wavefront.

For the wavefront exercise we had to draw the wave rays of circular, straight and irregular wavefronts.

We continued our unit, Waves in Two Dimensions. How exciting. Below is a diagram of how you would determine how the wavefronts are reflected at an angle to a straight barrier.

A few points to remember about this diagram are:

• The Incident wave ray is perpendicular to the Incident wavefront
• The Reflected wave ray is perpendicular to the Reflected wavefront.
• The normal is the straight line perpendicular to the barrier. (not in my diagram, but please bear with me)
• The angle of incidence (theta i) is the angle between the incident wave front and the barrier.
• The angle of reflection (theta r) is the angle between the reflected wavefront and the barrier.
• The angle of incidence is equal to the angle of reflection.
• Another thing you must remember is that the length between the lines of each wavefront should be equal in distance.

The diagram I drew above uses the angle of incidence and reflection as applied to the wavefronts to determine how the wavefronts are reflected.

Another method is to use the angle of incidence and reflection as applied to the normal. Therefore, the angle of incidence (theta i) would be the angle between the incident wave and the normal and the angle of reflection (theta r) would be between the reflection wave and the normal. I don't think we've used this method as of yet, but maybe we might later on.

We also looked at the reflection of waves from a Parabolic Reflector. We worked on drawing our own diagrams during the latter half of the class. We applied our knowledge of the straight barrier to help us out. The only difference is that it's a parabolic barrier.

Tonight's homework is our very first assignment in Waves of Two Dimensions. Complete it for tomorrow's class (or at least try to). ALSO don't forget our WAVES RESEARCH PROJECT due on September 25. Try not to leave it until the last moment like I know we've all done with one project or another. Good luck on that!

If you find anything confusing or anything wrong. Please leave a comment and let me know. This is my first time blogging for school where someone has to learn from it! I hope I didn't make any mistakes.

Last but not least, tomorrow's scribe will be... Mary Ann.

9/18/07

hello my name is Jennifer I am today's scribe.


Today we had a TEST on Waves In One Dimension 0_0
After the test we got a new green booklet called Waves in Two Dimensions & read up to page 6 we also got an exercise on Wavefront's to finish by tomorrow. That is all we did today (:


finally the scribe for tomorrow is . . .
LINA