How does light travel?

We are studying Energy and Its Properties, and throughout the week our young scientists have completed several labs to explore light's properties. 

During one lab, we tried to answer the question, How does light travel?  We taped a target to the wall, turned the lights out, and shined a flashlight on the target. We noticed light traveling out of the flashlight and we could see the light source on the target, however we couldn't see the beam of light as it traveled. In Trial 2, we repeated the experiment, but this time, we put a substance (baby powder) in the air. With the substance in the air, in the path of the light beam, we could see the light as it traveled from the flashlight to the target.  We had one more trick up our sleeve. In Trial 3, we repeated the steps from Trial 2, but this time we used a laser pointer. We recognized immediately that we could see the beam of light travel and that the light beam traveled in a straight line!  

 

Like all good scientists, we checked out theory with another lab. We used three index cards with an equal size hole in each, and lined them up  in a row, like the image shows. We put the flashlight up flush with in Card C and the light traveled through each card and hit the target. However, when we moved one of the index cards, the card would block the beam of light. We concluded that light travels in a straight line unless an object blocks the light beam.