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How light travels?
Light travels away from the source as a wave of energy.
How sound travels?
Sound waves are vibrating(振动)，They are longitudinal(纵向) waves and vibrations are backwards and forwards.
What is Refraction?
Refraction is the bending of light when it travels from one substance to another.
What is Reflection?
Reflection is when light bounces(弹回) off a surface.