# If light is a wave

1. May 14, 2005

### harhar

If light is a wave then how come we can hear around a corner but not see around a corner?

2. May 14, 2005

Diffraction is the key. This occurs when a wave passes through a gap OF A SIMILAR SIZE to the wavelength concerned. Sound waves diffract around doorways (similar size wave), but light doesn't as it has a wavelength of only a few hundred nanometers.

3. May 14, 2005

### ZapperZ

Staff Emeritus
Because the typical wavelength of visible light is waaaaaaay shorter than the typical wavelength of sound. It does mean that if you have EM radiation that has long wavelengths, it can go "around a corner", and voila, you have radio waves!

Zz.

4. May 14, 2005

### Galileo

The wavelength is sound is typically a few meters, long enough to bend around obstacles such as doors and hallways. Also, many sound sources emit sound more or less radially (in all directions).

Light sources are more often more beam-like and the wavelength of visible light is about 400 nanometers. You won't notice diffraction (the 'bending' of waves around corners) unless the obstacles have about the same dimensions as the wavelength. That's why we usually don't notice it, but if light passes through a small slit it does 'bend' and we can 'see around a corner'.