Monochromator, Beer's Law, Slits

Two types of monochromators:
A spectrophotometer uses a prism or grating to separate light.

A Prism: Dispersive prisms are used to break up light into its constituent spectral colours because the refractive index depends on frequency.

B Grating: A fundamental property of gratings is that the angle of deviation of all but one of the diffracted beams depends on the wavelength of the incident light. Therefore, a grating separates an incident polychromatic beam into its constituent wavelength components, i.e., it is dispersive. Because of their dispersive properties, gratings are commonly used in monochromators and spectrometers.

The slit width, expressed in millimeters, is a very important parameter and can affect your results both qualitatively and quantitatively.

The entrance slit is illuminated with   1,   2, and   3 only.  Entrance and exit slits are identical.  Plots on the right show changes in emitted power as the setting of monochromator is varied.”

The two basic quantitites that describe a light wave are the frequency f, of the wave (usually given in hertz, HZ, or cycles per second), and the wavelength,  . These quantities are related to each other and to the speed of light c.