The Photon Stream and Planck s Equation

Example 3-1 The frequency v of an electromagnetic wave is 4.4970x10 culate the corresponding wavelength X in nm and the radiant energy of this photon  

The energy of the 666.6 nm photon is extremely low, compared with the energy content of particular materials. For example, one barrel of petroleum (1 bbl= 158.9873 L, US petroleum) is equivalent to 5.8x10 J, and the annual commercial energy consumption of the world in 1996 was estimated to be about 327 x 10 J (vanLoon and Duffy, 2000). 

Using the molar Planck constant Np t (Tab. 3-1) it is possible to calculate the radiant energy of one mol of photons, i.e. of Na photons, according to Eq. 3-2  

This inverse proportional relationship between wavelength X and radiant energy 0 , of one mol of photons (Eq. 3-2) is graphically illustrated by Fig. 3-6. The radiant energy of one mol of photons is sometimes called the molar photon energy. 

The energy unit of photochemical reaction kinetics is one mol of photons (i.e. Na photons). In the photochemical literature it is often designated as hne einstein (Bolton, 1999), but this is not an lUPAC sanctioned unit. Therefore, the use of the unit einstein is discouraged. 

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