Like some others, I personally cannot sleep unless it is completely dark in my bedroom. However with the placement of my bed in a dark area of my room, I'm surprised to find that I cannot sleep because there is still light shining on my bed. But why is there still light if the window in my bedroom is behind my bed, next to a wall? Shouldn't the light be blocked by the barrier? No! The light from the window still shines on to my bed, despite the wall barrier and placement of the bed and window, because there is a diffraction of the light waves.
Diffraction occurs when light waves move past the edge of the barrier, bending the stream of light to another area. In my case, the light from my window was diffracting out past the wall barrier and around to the area where my bed is placed. The amount of diffraction of a light wave depends on both the wavelength of the wave and the size of the space the wave is traveling around. Because the wavelength of the light is constant and it is moving around a large space in my room, there is little diffraction.
Based on my research on diffraction, there is not much I can do about lessening the light shining onto my bed in my bedroom. Even if I were to make the space that the light waves pass through smaller, diffraction would still occur. However, I did learn what causes diffraction and what effects the amount it gives off. It seems that my only solution is to get some very good, very strong curtains!