Diffraction

Diffraction describes the change in direction of a wave as it travels between or around obstacles. It is similar to the reflection and refraction that implies a change in the direction of the waves when they encounter a change of medium. Reflection describes how waves bounce off surfaces. Refraction describes how bending waves as they pass through the boundary between two different media.

Diffraction is different. In diffraction, waves actually bend around objects in its path or bend through openings in between two barriers. You may have seen the diffraction occurs when water waves travel through a hole in a wall or a pier. Waves are bent out of the wall opening and the fan outward from the gap. To see how diffraction really works, let's first take a look at the sound waves.

Diffraction of Sound

It is easy to imagine the sound waves bend around obstacles. Have you ever tried to talk to someone who is standing in an adjacent room? Even if that person is not in your line of sight, usually you can hear at a reasonable volume. This is because their sound waves bend around the edges of the walls and doors to traveling to that person. The same happens when that person talks back to you.

Diffraction of sound waves is one reason that animals can communicate over long distances. Think of the places most animals live. Forests, mountains, grasslands, swamps and all have plenty of features of vegetation and earth blocking visual communication. Animals can still be in contact with each other because their vocalizations get beyond that. Their sound waves bend around obstacles and travel to your target audience.

Effects of Wavelength

Some animals are better at long distance communication than others. Elephants, for example, can communicate through miles of land in order to keep their herds together while they are traveling. People have not always known about elephant communication, and vocalizing at such low frequencies that can not even hear it. Elephants using infrasound, or sound waves with frequencies below 20 Hz. These low frequency, long wavelength diffraction actually sounds around objects in a greater than other sounds, HF grade. In fact, the amount of bending that occurs in any wave depends on the wavelength of the wave.

Think for a minute about why this might be true. In order for a wave to bend around an obstacle, the wavelength of the wave should be greater than the obstacle. The same is true for waves traveling through an opening. The wavelength must be greater than if the aperture to pass through the opening and out the other side. For any obstacle or given aperture, the waves with wavelengths longer wavelengths lean over the waves with wavelengths shorter wavelengths. If the wavelength is less than the obstacle or opening, then diffraction occurs hardly at all.