In this lesson you learned that light travels in straight lines. Suppose another student who has not taken this course asks you, 'How do you know that light travels in straight lines? After all, we cannot see light traveling. What's the evidence?' Briefly explain how you would respond to the student, first using pinholes as an example, and then using shadows as an example (You might consider what might have happened if light did not travel in straight lines.). (a) Using pinholes as an example: