I have always hated it when my parents came upstairs at night and turned on the hall light while I was trying to sleep. For some reason, the light from the hallway would somehow get into my room while the door was closed and make it brighter. I never knew why the light coming from a small source like from under a door or through a little hole would light up an entire room or look so much bigger and brighter than it originally seemed to be. This was until recently, when we learned about diffraction.
Diffraction is defined as the phenomenon that happens when a wave comes across an obstacle. What happens is when the waves pass through an opening, they spread out. The waves that get spread out the most are those that have the same wave length as the order of magnitude in the obstacle. The types of waves that can be diffracted can include sound, light, electromagnet (visible light), X-rays, and radio waves. Longer wavelengths and smaller objects help to provide maximum diffraction.
Therefore, when my parents turn on the hall light and my room is lit up even though the door is closed, it is because of diffraction. The light from the hall is traveling through that little slit underneath my door and the waves spread out into my room. This is caused because the light wave is coming in contact with an obstacle and when this happens, the light wave just goes around the obstacle (my door) and spreads out which causes my whole room to light up.