true or false?
1.light rays could be blocked,and they could pass throught all types of materials since they travel on a straight line?
2.optical fibers can be used in communication,in industry,and medecine
3.light travels in a curve line when it passes throught a single medium.
4.the sun is the main source of natural light.
5.light travels slower in the air than througt water because air is less dense than water
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