Diffraction occurs when a wave bends around an obstacle or spreads through an opening.
Radio waves (especially AM) diffract when they encounter buildings. The radio waves bend around the building and the reception is still good on the opposite side. There is no “shadow” of the radio wave.
diffract when they pass through a door. The sound spreads and fills the room on the other side of the door. Try standing out in the hallway by your classroom and talk. Can the people inside the class hear you? This is diffraction.
You can see visible light waves diffract through curtains. Look out at a street lamp. The light will spread left and right and up and down. This occurs because the light diffracts when it goes through the weave of the curtain.
You may also notice that the light is alternately bright and dark as you look through the curtain. This is from . The bright places are where light waves are adding together. The dark places are where the waves cancel. With visible light, interference always occurs with diffraction.
