Lesson 10 Key Concepts

Different light sources produce different spectra. 1. Different light sources produce different spectra.

2. The spectrum produced by a luminous object is determined by the wavelengths of light emitted by the object.

Spectroscopy can be used as an analytical tool. (identify substances) 3. Spectroscopy can be used as an analytical tool. (identify substances)

4. Different light sources produce different spectra in which some colors and wavelengths found in sunlight may be absent.

Lesson 10 Notes

1. Diffraction grating: tiny sheet of transparent plastic that has thousands of tiny parallel plastic groove s carved into its surface. Each groove diffracts light over a wide range of angles. Example: Diffraction occurs when a wave meets the edge of an obstacle (Lesson 7).

2. Amount of deflection depends on distance between the grooves on the diffraction grating and the wavelength of light striking the grating. Diffraction gratings separate a beam of light (white light) by its wavelength or color. However; only a particular wavelength will be reinforced; the rest will cancel each other out. Diffraction grating will produce a more defined spectrum than the prism due to spectral resolution – separating power due to groove spacing.

3. Lab results: Daylight – continuous spectrum with all the “colors of the rainbow.” Incandescent lightbulb – continuous spectrum but bright in red and orange. Compact Fluorescent lightbulb – discontinuous spectrum showing R- O-G-B w/ black lines – which mean???

4. Why spectra differ: Different glowing materials Different methods of producing light Temperature of the light source Amount of energy emitted Each gas has its own spectrum – aka fingerprint