Index of refraction n

Transcription

1 Refraction 1

2 Refraction Cause 2

3 Index of refraction n In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air Others corn oil glycerol Lucite Zircon ~

4 Refraction examples Draw the refracted ray In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air ~ 1.0 Lucite Others corn oil glycerol Lucite Zircon 1.92 Zircon Corn oil Water In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air ~ 1.0 Corn oil Others corn oil glycerol Lucite Zircon 1.92 Glycerol Water In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air Others corn oil glycerol Lucite Zircon ~ air 4

5 Refraction applications Spearfishing Stars 5

6 Refraction Student Sheet 1. When light passes from a more optically dense medium into a less optically dense medium, it will bend (towards, away from) the normal. 2. When light passes from a medium with a low index of refraction value into a medium with a high index of refraction value, it will bend (towards, away from) the normal. 3. In each diagram, draw the "missing" ray (either incident or refracted) in order to appropriately show that the direction of bending is towards or away from the normal. 4. Arthur Podd's method of fishing involves spearing the fish while standing on the shore. The actual location of a fish is shown in the diagram below. Because of the refraction of light, the observed location of the fish is different than its actual location. Indicate on the diagram the approximate location where Arthur observes the fish to be. Must Arthur aim above or below where the fish appears to be in order to strike the fish 5.) The sketch shown here shows a light ray moving from air into water at a 45 degree angle to the normal. Which of the three rays indicated with capital letters is most likely the light ray that continues inside the water 6

7 6.) The sketch shown here shows a light ray moving from glass into air at a 30 degree angle to the normal. Which of the three is most likely the light ray that continues in the air 30 7.) The sketch shown here shows a light ray moving from air into glass at an angle of 40 degrees to the normal. Which of the three rays is most likely the light ray that travels in the air after emerging from the opposite side of the block? Sketch the path of the ray inside the block 8.) The sketch shown here shows a light ray moving from water into a rectangular air block at 40 degrees to the normal. Which of the three rays is most likely the light ray that continues into the water on the opposite side? Sketch the path of the ray inside the block 9.) As the light ray above travels from water to air and then water again. What happens to the speed of the light? The wavelength of the light? And the frequency of the light? 7

8 Index of refraction calculations n = c / v v = f λ DERIVATION Moving from medium 1 to medium 2... the f is the same in both mediums, the v and λ change.... set f 's and sub in equations above to obtain n 1 λ 1 = n 2 λ 2 1.) What is the speed of light in flint glass In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air ~ 1.0 Others corn oil glycerol Lucite Zircon 2.) If the wavelength of light in air is 589 nm, what is frequency of light in alcohol, what is the wavelength in alcohol ) The speed of light in an unknown material is 63 x 10 8 m/s. What is the material? 8

9 Calculating Refraction Angles n i (incident medium the one you start in) n r (refracted medium the one you end in) 9

10 4.) A ray of light travels between lucite and alcohol. The angle of incident between the two layers is 10 degrees. Determine the angle of refraction and the speed of the light in alcohol. In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air Others corn oil glycerol Lucite Zircon ~

11 5.) Light traveling in air hits and unknown medium at an angle of incidence of 40 degrees. The angle of refraction in the new medium is degrees. What is the new medium In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air Others corn oil glycerol Lucite Zircon ~

12 6.) Three different materials. (a) By investigation, which of the three materials is most optically dense (b) The top material is either air or diamond, and the bottom material is also either air or diamond. Which is which? (c) Determine what the middle material is (d) find the angle of refraction in the bottom material In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air Others corn oil glycerol Lucite Zircon ~ (e) Which material does the light have the largest speed in? the largest frequency in? the largest wavelength in? 12

13 Mirage 13

14 Blue Red Sky 14

15 Dispersion Revisited 15

16 Total Internal Reflection 16

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19 Finding θ c, the critical angle. 19

20 7.) What is the critical angle for light traveling from alcohol into air In texbook n values 8.) Sketch the path of the light ray shown below. Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air Others corn oil glycerol Lucite Zircon ~ In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air Others corn oil glycerol Lucite Zircon ~

21 9.) You are on the bottom of the ocean and want to send a signal with a light beam to a hotty mermaid colony but there is a coral reef in the way. Using your physics skilz, calculate the angle at which you would have to aim your flashlight to bounce the beam to the mermaid colony on the other side. 21

22 10.) A light ray travels from ice into an unknown substance and then towards and air layer on top. The light ray hits the first surface at an angle of 53 away from the normal line. (the substance can be a solid, liquid or gas) (a) It is observed that the light ray slows down to x 10 8 m/s when it enters the substance. What is this substance? (b) Will the ray bend away from or towards the normal line as it enters the substance? (c) Find the angle of the refracted ray in the substance (d) Draw a sketch this situation clearly showing the light ray moving in the ice and the light ray moving in the substance with all angles labeled properly. (e) Finish the sketch you created in part d by determining what will happen to the light as it hits the air boundary. In texbook n values Diamond Flint Glass Crown Glass Fused quartz Ice Benzene Ethyl Alcohol Water Carbon Dioxide Air Others corn oil glycerol Lucite Zircon ~

23 Special Situations DATE: 04/27 23

24 Thin Films recall boundary behavior less dense more dense more dense less dense 24

25 Two light waves very close together would interfere 25

26 Two light waves very close together would interfere 26

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28 Anti reflective coating 28

29 The key to analyzing thin films relies on four important ideas to look at. Path difference medium 1 film Film λ medium 2 Thickness of Film Boundary Conditions Note: To see a specific color, you need to reinforce that wavelength color (need constructive interference for that wavelength range) 29

30 Example 30

31 1.) A thin layer of oil (n=1.2) rests on a water surface (n=1.33). A 100 nm light wave in air is incident on the film (a) What minimum thickness would reinforce the reflection (b) What minimum thickness would suppress the reflection? 31

32 2.) A 500 nm light wave traveling in air enters a thin soap film (n=) surrounded by air. (a) If the film is nm thick will a reflection be suppressed or reinforced (b) What minimum film thickness with reinforce the reflection? 32

33 3.) A 240 nm thick coating (n=1.25) is placed on a glass lens (n=1.66). What maximum wavelength of light in air would reinforce the reflection? 33