હવે, \({E_g} = \,\,\,\frac{{hc}}{\lambda }\,\,\,\,\)

\(\therefore \,\,\,\lambda \,\, = \,\,\frac{{hc}}{{{E_g}}}\,\, = \,\,\frac{{6.62\,\, \times \,\,{{10}^{ - 34}} \times \,3\,\, \times \,\,{{10}^8}}}{{2.5\,\, \times \,\,1.6\,\, \times \,\,{{10}^{ - 19}}}}\,\,\, = \,\,4.965\,\, \times \,\,{10^{ - 7}}\,m\,\, = \,\,4965\,\,\mathop A\limits^ \circ  \)

એટલે કે ફોટો-ડાયોડ \(4000 Å\) તરંગલંબાઈ ધરાવતા વિકિરણને પારખી શકશે.