Diffraction Grating
Aim
To investigate how the diffraction grating can be used to measure the wavelength’s of light.
Abstract
To determine the wavelengths of the visible spectral lines of Ne with high precision and to compare calculated with handbook values. To determine the experimental uncertainty of the wavelength values (i.e. the precision of the experiment). To observe the line spectrum of an unknown source and determine the wavelengths of one particular order.
Theory
Figure 1
Figure 1
Light can be split up into a range between 400 nm to 700nm, this is called the visible spectrum, which is part of the electromagnetic spectrum. The largest of the visible spectrum is red which is about 700 nm and the smallest wave is violet which is approximate 400 nm. From figure 1 it can be seen the colours of light being separated by a triangular prism the longer waves (red) and shorter waves (blue) being separated.
Diffraction, when waves meet a gap in a barrier they carry on through the gap, the waves spread out to wide extent into the area beyond the gap, as can be seen in figure 2. But the extent on how it does spread depends on the size of the gap, the larger the gap the less spreading which is done by the wave, the smaller the gap the more spreading the waves does. This exact phenomenon is the reason you can hear someone round the corner of a building before you see them or while driving your car you can still receive a radio signal miles away from the transmitter.

Figure 2
Figure 2

When light passes through a small slit it can be seen pattern starts to emerge with a bright central region, and alternating light and dark bands. If the light is the same colour throughout the bands will be of the same colour. Red light has a broader pattern than blue light, suggesting that the diffraction effect increases with wave length. If we use white light, the