Table 1 shows the radiant power distribution of a 150-W metal halide lamp. Waveband (nm) Radiant power (W) 450 - 500 8.X 500-550 10.X 550 - 600 14.0 600-650 5.6 Table 1 Radiant power distribution X=4 The lamp is housed in a spotlight with a light output ratio of 0.7X. The spotlight produces a spot with a diameter of 80 cm when it is placed 5 m vertically above the spot. A number of spotlights are used to provide 2X0 lux on a building faade with dimensions of 10 m x 30 m high. The spectral efficiency for photopic vision is given by V(x) = sin [(1 380)/350], where i is in nm. The maximum luminous efficacy is taken to be 683 lm/W at 555 nm. (a) Evaluate the luminous efficacy of the spotlight. (b) Find the luminous intensity of the spotlight. (c) Calculate the luminance of the spot when viewing vertically above the spot. The spot reflects 7X% of luminous intensity from the spotlight. (d) Find the number of spotlights required if 8X% of their luminous flux can fall on the faade. Table 1 shows the radiant power distribution of a 150-W metal halide lamp. Waveband (nm) Radiant power (W) 450 - 500 8.X 500-550 10.X 550 - 600 14.0 600-650 5.6 Table 1 Radiant power distribution X=4 The lamp is housed in a spotlight with a light output ratio of 0.7X. The spotlight produces a spot with a diameter of 80 cm when it is placed 5 m vertically above the spot. A number of spotlights are used to provide 2X0 lux on a building faade with dimensions of 10 m x 30 m high. The spectral efficiency for photopic vision is given by V(x) = sin [(1 380)/350], where i is in nm. The maximum luminous efficacy is taken to be 683 lm/W at 555 nm. (a) Evaluate the luminous efficacy of the spotlight. (b) Find the luminous intensity of the spotlight. (c) Calculate the luminance of the spot when viewing vertically above the spot. The spot reflects 7X% of luminous intensity from the spotlight. (d) Find the number of spotlights required if 8X% of their luminous flux can fall on the faade