31. Kosmos 60 measured the gamma-ray background flux density to be 1.7?0 4 quanta / ( m 2 �s ). 32. AB magnitude is defined so that the zero point corresponds to a bandpass-averaged spectral flux density of 3631 Jansky: 33. At a point within a collimated beam, the spectral flux density vector has a value equal to the Poynting vector, 34. Gaussian units, flux density " is " the very same as electric field in free space, not just a scaled copy. 35. There are two main approaches to definition of the spectral flux density at a measuring point in an electromagnetic radiative field. 36. This is because the internal magnetic domains of the material align with each other to greatly enhance the magnetic flux density . 37. This means, that when the product \ sigma \ lambda _ s is positive, the flux density B increases under stress. 38. Sometimes it is more convenient to display graphical spectra with vertical axes that show the "'relative spectral flux density " '. 39. In this case, the spectral flux density at a given wavelength is expressed as a fraction of some arbitrarily chosen reference value. 40. On the other hand, when the product \ sigma \ lambda _ s is negative, the flux density B decreases under stress.
