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Problem 58 Hard Difficulty

Given small samples of three liquids, you are asked to determine their refractive indexes. However, you do not have enough of each liquid to measure the angle of refraction for light refracting from air into the liquid. Instead, for each liquid, you take a rectangular block of glass ($n$ = 1.52) and place a drop of the liquid on the top surface of the block. You shine a laser beam with wavelength 638 nm in vacuum at one side of the block and measure the largest angle of incidence $\theta_a$ for which there is total internal reflection at the interface between the glass and the liquid ($\textbf{Fig. P33.58}$). Your results are given in the table:

What is the refractive index of each liquid at this wavelength?

Answer

$$1.40$$

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Top Physics 103 Educators
Christina K.

Rutgers, The State University of New Jersey

Farnaz M.

Other Schools

Zachary M.

Hope College

Meghan M.

McMaster University

Video Transcript

to solve this question, we have to relate. Teacher A With the refraction index, it's off liquids A, B and C. We begin by remembering that a total internal reflection is the same as an angle off refraction off 90 degrees. Therefore, in these interface between liquid and gas, the refraction angle is 90 degrees, so we can apply Snell's law there by using Snell's law. There we get that the refraction index off the liquid times this sign off the angle of refraction. Izzy Kohstuh refraction index off glass times the incident angle which, according to my drawing and Steve the seat, notice that our is 90 degrees on the sign off. 90 is one. So these is equals to one and we get n equals two and glass times this sign off the angle off incidence. No, As you can see from the figure, we can do this on the normals, meet at a 90 degree angle. The reform you can see that t to C and T Toby are such that they at 90 degrees. Then this sign off details see is equals to the co sign off the meat. So the index off a fraction off the liquid is the index off infraction off glass times they curl. Sign off, detail me. And now we have to relate. Victor, be with Tito A. In order to do that, we have toe applies now's law in these interface. By doing that, we get the following the index of refraction off air times. The angle off incidents teeter a is equals to the index off refraction off less times the sign off the angle of refraction in these cases, Toby. Then notice that an air is in question. Well, so we can solve this equation for the sign off. To me down the sign off the baby is equal to the sign off detail. Eight. Divided by the refraction index off glass. Using this equation, we can calculate it'll be for each off these three liquids and then using the value off it'll be, we can calculate device off the refraction index. Before doing that. Let me organize my board for liquid A. The sign off it'll be is equals to the sign off 52 degrees divided by 1.50 truth, and these results in an angle theta be off approximately 31 point to true six degrees. Then the refractive index off liquid A is given by 1.50 truth times. They have signed off 31.2 to 6. These results seen approximately one 0.3. Now for a liquid B, we have the sign off. The Derby equals to the sign off 44.3 degrees, divided by 1.50. Choose these results in an angle. Tita, be off approximately 27 points. 35 38 degrees. Then they refractive index off. With me, it's 1.53 times They cursed Sign off 27.35 38 which results in approximately 1.35 now for liquid. See, we have sign off. It'll be being equal to the sign off 36.3, divided by 1.50 troops. The results in Tita be off approximately 22 0.922 degrees show. Their refractive index off liquid see is 1.52 times the co sign off 22.922. The results in an attractive index off approximately one 0.4 leases down. Start to this question

Brazilian Center for Research in Physics
Top Physics 103 Educators
Christina K.

Rutgers, The State University of New Jersey

Farnaz M.

Other Schools

Zachary M.

Hope College

Meghan M.

McMaster University