Cuesta College, San Luis Obispo, CA
Originally uploaded by Waifer X
Glass rods suspended in air, then dropped down into oil. Display at the Arizona Museum of Science, Phoenix, AZ. Video by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.
Students have a weekly online pre-lab assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lab, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the lab instructor at the start of the following lecture.
Watch the video link below, where glass rods suspended in air are then dropped into oil. The index of refraction of the glass rods should be:
(A) close to the index of refraction of air.
(B) between the indices of refraction of air and oil.
(C) close to the index of refraction of oil.
(D) (Could not get the video link to work.)
(E) (I'm lost, and don't know how to answer this.)
(A) : 0 students
(B) : 1 student
(C) : 9 students
(D) : 1 student
(E) : 1 student
Briefly explain your answer to the previous question (comparing n_glass to n_air or n_oil). (Graded for completion.)
The following are all of the student responses to this question, verbatim and unedited.
"The glass rods would be between air and oil because air is 1.000293 and oil is 1.52045 the glass rods fall in between those limits"
"The glass rods appear to be transparent in the oil, so the index of refraction of the rods would be closest to the index of refraction of the oil. Light is going through both instead of bouncing off of the glass rods like they do in air"
"if the n of the the glass where more or less than the oil there would be noticable light travel changes. The n of both materials is close to equal the lights can bend in same manner for both."
"The point of view is not parallel to the bars and is hard to tell which way the light is bending."
"It disappears when dropped in oil. Only light that travels through the air in the center of the rods is distorted and visible in the oil."
"The index of refraction of glass is approximately 1.4-1.6 depending on the type of glass, the index of air is approximately 1, and the index of silicone oil is 1.5. Therefore I expect the glass rods to be close to the index of refraction of oil versus air."
"When dipped into the oil, the class rod becomes barely visable, meaning that the index of refration for the glass rod and oil are very close together."
"the index of refraction of the glass rods should be close to the index of refraction of oil because it was near transparent and the light rays didn't change direction."
"The rods are very visible when suspended in air. You can clearly see their shape and size. However, when they are lowered into the oil it becomes difficult to seem them. This is because they have a much different index of reflection than air so the light bends significantly as it passes through. They have a similar index of refraction as oil because when suspended in the oil the light is barely bent thus making it difficult to see them."
"When the glass was suspended in the oil it could barely be detected, but when the glass was suspended in the air it was easy to see it. Therefore the glass has an index of refraction that is closer to the oil than the air."
"Because it becomes so much harder to see the glass rods in oil, the n_glass and n_oil must be more similar than n_glass and n_air."