A wave of light has a wavelength, defined as the distance from one crest of the wave to the next, and written using the symbol . The wavelengths of visible light are quite small: between 400 mm and 650 nm, where 1 nm = 10-9 m is a ``nanometer'' - one billionth of a meter. Red light has long wavelengths, while blue light has short wavelengths. A particle of light, known as a photon, has an energy E. The energy of a single photon of visible light is tiny, barely enough to disturb one atom; we use units of as eV, to measure “electron-volts”, abbreviated the energy of photons. Photons of red light have low energies, while photons of blue light have high energies. The energy E of a photon is proportional to the wave frequency ѵ, E = h ѵ where the constant of proportionality h is the Planck's Constant, h = 6.626 x 10-34 J s. Also, the relationship between frequency and wavelength can be defined as: = c ѵ λ where c is the speed of light (3×108 metres per second). So photons still have a wavelength. A famous result of quantum mechanics is that the wavelength relates to the energy of the photon. The longer the wavelength, the smaller the energy. For instance, ultraviolet photons have shorter wavelengths than visible photons, and thus more energy. This is why they can give you sunburn, while ordinary light cannot. Spectra can be simplified to one of three basic types. Simple examples in the visible wavebands are shown below: Type of Spectrum Photographic example Continuous (or continuum) Absorption (dark line) Emission (bright line) One means by which a continuous spectrum can be produced is by thermal emission from a black body. This is particularly relevant in astronomy. Astronomical spectra can be combination of absorption and emission lines on a continuous background spectrum. The important thing to know about absorption and emission lines is that every atom of a particular element will have the same pattern of lines all the time. And the spacing of the lines is the same in both absorption and emission, only emission lines are added to the continuum, while absorption lines are subtracted.
A wave of light has a wavelength, defined as the distance from one crest of the wave to the next, and written using the symbol . The wavelengths of visible light are quite small: between 400 mm and 650 nm, where 1 nm = 10-9 m is a ``nanometer'' - one billionth of a meter. Red light has long wavelengths, while blue light has short wavelengths. A particle of light, known as a photon, has an energy E. The energy of a single photon of visible light is tiny, barely enough to disturb one atom; we use units of “electron-volts”, abbreviated as eV, to measure the energy of photons. Photons of red light have low energies, while photons of blue light have high energies. The energy E of a photon is proportional to the wave frequency ѵ, E = h ѵ where the constant of proportionality h is the Planck's Constant, h = 6.626 x 10-34 J s. Also, the relationship between frequency and wavelength can be defined as: ѵ = c λ where c is the speed of light (3×108 metres per second). So photons still have a wavelength. A famous result of quantum mechanics is that the wavelength relates to the energy of the photon. The longer the wavelength, the smaller the energy. For instance, ultraviolet photons have shorter wavelengths than visible photons, and thus more energy. This is why they can give you sunburn, while ordinary light cannot. Spectra can be simplified to one of three basic types. Simple examples in the visible wavebands are shown below: Type of Spectrum Photographic example Continuous (or continuum) Absorption (dark line) Emission (bright line) One means by which a continuous spectrum can be produced is by thermal emission from a black body. This is particularly relevant in astronomy. Astronomical spectra can be combination of absorption and emission lines on a continuous background spectrum. The important thing to know about absorption and emission lines is that every atom of a particular element will have the same pattern of lines all the time. And the spacing of the lines is the same in both absorption and emission, only emission lines are added to the continuum, while absorption lines are subtracted.
Flame_Tests,_Atomic_Spectra___Applications_Activity_new_2015.docx