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NaiveAbafar3712

I need to explain why when we look at a laser ray, we can't see its trajectory, but when chalk powder floats in the air in front of it, we can suddenly see the ray. Can anyone help me? Thank you! 

Emilie L

Hello NaiveAbafar3712,

Thanks for reaching out! Let me help you. 

This phenomenon is explainable with the light trajectory. 

In order to see a laser ray, an observer must be in front of the ray as light travels in a straight trajectory. Therefore, when chalk powder or any other object or particle passes in front of the ray, a diffuse reflection happens. In other words, the straight incident ray is reflected and scattered all over the place making it possible for, any observer, no matter where they stand to see it. 

Here's a representation of a diffuse reflection 

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Hope that helps! 

Let us know if we can do anything else! 

Emilie