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Name: Ja
Status: student
Grade: 6-8
Location: OH
Country: USA
Date: 4/1/2005


Question:
Why does objects in water sometimes look smaller and then sometimes look bigger? I know it is due to the water refracting light, but sometimes, if there is a golf ball in the middle of the globe, and then there is a empty space of air, then there is a layer of glass with water and finally, there is the last layer of glass, the golf ball inside appears to be smaller than real life than normal, or even bigger. Why is that?


Replies:
I assume in this case you are talking about looking through the bowl at the golf ball. In this case, the entire bowl of water is acting like a magnifying glass. The increased density (and the associated difference in actual speed of light) causes light to diffract (bend) creating this illusion.

Ryan Belscamper


Ja,

When light passes through materials with curved shapes, the light can change direction. Your eyes tell how tall something is by light from the top and light from the bottom of the object. If light from the top and the bottom are both coming from almost the same directions, the object looks small. If they come from very far apart directions, the object looks large. When the light changes directions, light from the top and light from the bottom can appear to come from very far apart directions, or very close together directions, when really they do not. This makes the size look different than what it really is.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College


This is a questions from:

Paul Hewitt "Conceptual Physics" Addison-Wesley

The helicopter leaves the ground with the ground's eastward velocity. It maintains that velocity unless acted upon by an external force. So the point of departure and the helicopter are both moving eastward at the same rate. The aircraft appears to hover.

---Nathan A. Unterman



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