Analysing Diffraction of Waves

1. Diffraction of waves is a phenomenon in which waves spread out as they pass through an aperture or round a small obstacle.

Source: http://www.launc.tased.edu.au/online/sciences/physics/diffgaps.gif

2. The effect of diffraction is obvious only if

a) the size of the aperture or obstacle is small enough.
b) the wavelength is large enough

3 Characteristics of diffracted waves:

a) Frequency, wavelength and speed of waves do not change.
b) Changes in the direction of propagation and the pattern of the wave.

Diffraction of Light

1. Light is diffracted if it passes through a narrow slit comparable in size to its wavelength.
However, the effect is not obvious as the size of the slit increases. This because the wave-lengths of light are very short.

2. Diffraction of light is hardly noticeable compared with diffraction of sound waves and water waves because the wavelength of light is very short or small (approx: 10-7 m)

3. Light waves will be diffracted if

a) Light is propagated through a pin hole or a tiny slit where its size is similar to that of the light wavelength (around one hundredth of a millimetre or less)

b) the light source is monochromatic, i.e. light of one colour, and therefore one wavelength only.