Based on what you know about how light travels, explain why you can't see the back of your own head without using a mirror, camera or other device

Light travels in straight lines, a principle known as rectilinear propagation. This is the fundamental reason why we can't see the back of our own head without the aid of a mirror or other device.

Here's a step-by-step explanation:

1. When light hits an object, it bounces off in all directions. Some of this light enters our eyes, which is how we see the object.

2. The back of our head is an object like any other. Light hits it and bounces off in all directions.

3. However, the light that bounces off the back of our head travels away from our eyes, not towards them. Because light travels in straight lines and our eyes are in front of our head, not behind it, this light doesn't reach our eyes.

4. Therefore, we can't see the back of our own head.

5. If we use a mirror, the light bouncing off the back of our head can hit the mirror and be reflected towards our eyes. This allows us to see the back of our head.

6. Similarly, a camera can capture the light bouncing off the back of our head and display it on a screen that we can see.

So, the reason we can't see the back of our own head without a mirror, camera, or other device is because of the way light travels.