Unit: Waves
Year: 1992 Question#: 43
Question: The Diagram below represents a light ray passing from corn oil into medium X with no change in in velocity.
In this diagram, medium X could be
(1 ) water
(2 ) diamond
(3 ) glycerol
(4 ) alcohol
What is this question really asking?
Explanation by: Liz M.
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Answer 1
Water
INCORRECT
This answer is incorrect. In order to answer this question, one must consult the Absolute Indices of Refraction section of their Reference Table For Physics. As the light ray passes from the corn oil into medium X it is evident that angle "i" and "r" are equal. For this to be true, the absolute index of refraction of corn oil and medium X must be the same. When consulting your reference table, you will see that water has 1.33 as it's absolute index of refraction and corn oil has 1.47 as it's absolute index of refraction. Since water's is smaller than corn oil, the light ray would travel faster resulting in it bending away from the normal line (the dotted line in picture). Therefore, water cannot be correct. return to top
Answer 2
diamond
INCORRECT
This answer is incorrect. In order to answer this question, one must consult the Absolute Indices of Refraction section of their Reference Table For Physics. As the light ray passes from the corn oil into medium X it is evident that angle "i" and "r" are equal. For this to be true, the absolute index of refraction of corn oil and medium X must be the same. When consulting your reference table, you will see that diamond has 2.42 as it's absolute index of refraction and corn oil has 1.47 as it's absolute index of refraction. Since diamond is more, the light ray should bend towards the normal line (dotted line in diagram) upon entering medium X. return to top
Answer 3
glycerol
CORRECT
This answer is correct. In order to answer this question, one must consult the Absolute Indices of Refraction section of their Reference Table For Physics. As the light ray passes from the corn oil into medium X it is evident that angle "i" and "r" are equal. For this to be true, the absolute index of refraction of corn oil and medium X must be the same. When consulting your reference table, you will see that glycerol has 1.47 as it's absolute index of refraction and corn oil has 1.47 as it's absolute index of refraction. You will note that these are the same. This meaning that the light ray could pass throught the medium with no change in direction. return to top
Answer 4
alcohol
INCORRECT
This answer is incorrect. In order to answer this question, one must consult the Absolute Indices of Refraction section of their Reference Table For Physics. As the light ray passes from the corn oil into medium X it is evident that angle "i" and "r" are equal. For this to be true, the absolute index of refraction of corn oil and medium X must be the same. When consulting your reference table, you will see that alcohol has 1.36 as it's absolute index of refraction and corn oil has 1.47 as it's absolute index of refraction. Since alcohol is smaller than corn oil, the light ray is traveling faster and should bend further away from the normal line (dotted line in diagram). Therefore, alcohol could not be medium X. return to top