How Do You Make a Spectrograph?
There are two very different ways to measure spectra.
In the first class of instruments, scientists use the wave-like nature
of electromagnetic radiation.
A prism bends the incoming light (refraction), and how
How Do You Make a Spectrograph?
There are two very different ways to measure spectra.
In the first class of instruments, scientists use the wave-like nature
of electromagnetic radiation.
A prism bends the incoming light (refraction), and how much it bends depends
on the wavelength. Using a slit to block out any unwanted light, place a
prism behind the slit, and record the image (using a photographic plate,
for example, or an electronic camera). The position along one direction
of the image corresponds to the wavelength. The combination of a dispersive
element (something that divides light into its component wavelength, the prism
in this case) and an imaging detector makes a spectrograph.
Instead of a prism, you can use a grating (a grating makes use of diffraction,
another property of waves) as the dispersive element. In fact, this is
more common in modern spectrographs.
In the second class of instrument, scientists use the particle-like
nature of electromagnetic radiation. Each photon (a packet of radiation)
carries a certain