3.4) Viewed through a spectroscope, the spectrum of the light from the bulb would show the familiar rainbow of colors, from red to violet, without interruption, as presented in Figure 4.2(a).įigure 4.2 When passed through a slit and split up by a prism, light from a source of continuous radiation (a) gives rise to the familiar rainbow of colors. A light bulb, for example, emits radiation of all wavelengths (mostly in the visible range), with an intensity distribution that is well described by the blackbody curve corresponding to the bulb's temperature. The spectra we encountered in Chapter 3 are examples of continuous spectra. Because different wavelengths of electromagnetic radiation are diffracted by different amounts as they pass through a narrow gap, the effect of the grating is to split a beam of light into its component colors. The spaces between the lines act as many tiny openings, and light is diffracted as it passes through them. In many large instruments the prism is replaced by a device called a diffraction grating, consisting of a sheet of transparent material with many closely spaced parallel lines ruled on it. The resulting spectrum can be viewed through an eyepiece or simply projected onto a screen. The light passes through a prism and is split up into its component colors. A small slit in the mask on the left allows a narrow beam of light to pass.
Despite their greater sophistication, however, their basic operation is conceptually similar to the simple spectroscope shown in the figure.įigure 4.1 Diagram of a simple spectroscope.
#Sodium emission spectrum professional#
The research instruments (called spectrographs, or spectrometers) used by professional astronomers are rather more complex, consisting of a telescope (to capture the radiation), a dispersing device (to spread it out into a spectrum), and a detector (to record the result). In its most basic form, this device consists of an opaque barrier with a slit in it (to define a beam of light), a prism (to split the beam into its component colors), and an eyepiece or screen (to allow the user to view the resulting spectrum). Radiation can be analyzed with an instrument known as a spectroscope. Because spectra are so important, let's examine in more detail how astronomers obtain and interpret them. Far from invalidating our earlier studies, however, these deviations contain a wealth of detailed information about physical conditions in the source of the radiation. 3.4) All spectra deviate from this idealized formsome by only a little, others by a lot. But in reality, no cosmic object emits a perfect blackbody spectrum like those discussed earlier. A vital step in this process is the formation of a spectrumsplitting the incoming radiation into its component wavelengths.
In Chapter 3 we saw something of how astronomers can analyze electromagnetic radiation received from space to obtain information about distant objects.
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