All Problems Photometry and Geometrical Optics
Problem 5.2
A point isotropic source emits a luminous flux \(\Phi=10 \mathrm{~lm}\) with wavelength \(\lambda=0.59 \mu \mathrm{m} .\) Find the peak strength values of electric and magnetic fields in the luminous flux at a distance \(r\) \(=1.0 \mathrm{~m}\) from the source. Make use of the curve illustrated in Fig. 5.1 .
\[ \text { 5.2. } E_{m}^{2}=V \overline{\mu_{0} / \varepsilon}_{0} A \Phi / 2 \pi r^{2} V_{\lambda}, \text { hence } E_{m}=1.1 \mathrm{~V} / \mathrm{m}, \quad H_{m}= \] \(=3.0 \mathrm{~mA} / \mathrm{m} .\) Here \(A=1.6 \mathrm{~mW} / \mathrm{lm}, V_{\lambda}\) is the relative spectral response of an eye for the given wavelength.