Illuminance A spotlight with intensity 5000 candles is located 15 feet above a stage. If t...

Illuminance A spotlight with intensity 5000 candles is located 15 feet above a stage. If the spotlight is rotated through an angle θ as shown in the figure, the illuminance E (in foot-candles) in the lighted area of the stage is given by

where s is the distance (in feet) that the light must travel.

(a) Find the illuminance if the spotlight is rotated through an angle of 30°.

(b) The maximum illuminance occurs when θ =0°. For what value of θ is the illuminance one-half the maximum value?

EXERCISE