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Refraction

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Question 1 0:29
  • Question 5 1:03
  • Question 6 1:24
  • Question 7 2:01

Transcription: Refraction

Hi everyone and welcome back to Educator.com. 0000

In this mini-lesson, we are going to go through page 1 of the worksheet on refraction from the APlusPhysics site. 0003

And you will find the link to that down below the video. 0009

Now as we go through these questions, we are not going to go through 2-4 here in our review, just because they are -- the do not lend themselves well to doing these on video with the requirement for a protractor and drawing things to scale, so I will let you guys do those on your own. 0012

We are just going to skip through 2-4. 0026

So diving into Number 1. 0029

In which way does blue light change as it travels from diamond into crown glass? 0031

Well to do this one, you need to know that the index of refraction of diamond is 2.42 and the index of refraction of crown glass is about 1.52, so those would be good things to look up beforehand or to use a table to look up. 0035

What happens as you go from high index to low index materials? 0049

You go from a lower speed to a higher speed. 0053

Speed is going to -- Number 4, Increase. 0055

Now, on to Number 5 -- A change in the speed of a wave as it enters a new medium, produces a change in -- well V = F(λ) and as the wave enters a new medium, frequency stays the same, so a change in the speed is going to produce a change in the wavelength. 0062

So answer to number 5 must be Number 3. 0079

Number 6 -- The diagram below represents a ray of monochromatic light at a frequency of 5.09 × 1014 Hz passing from medium (x) and equals 1.46 in diffused quartz and equals 1.46. 0084

What path will the ray follow in the quartz? 0097

Well, if we have the same index of refraction on both sides of the boundary, then our wave is not going to change speed. 0100

It is not going to speed up or slow down, so it is not going to bend. 0108

We are just going to follow the same path in as out, so if no bending, the answer must be Number 3, C. 0111

Last one on this page. 0119

A straight glass rod appears to bend when placed in a beaker of water as shown in this diagram. 0122

What is the best explanation for this phenomena? 0127

The water is warmer than air, though it could be, but it does not have a whole lot to do with the bending of the straw. 0130

Light travels faster in water than air. Well, no it slows down in water. 0136

Light is reflected at the air-water interface. 0140

Well, yes, some of the light is reflected there and some is transmitted, but that does not explain the bending. 0143

Light is refracted; it is bent as it crosses the air-water interface. 0148

There is our answer. 0152

All right, just a very quick review of that one page of the worksheet on refraction. 0154

If that went well -- Terrific -- keep moving on to more complicated problems, if it did not, it is a great opportunity to go back and review refraction. 0159

Thanks everyone for your time. Make it a great day!0167