Home examination tasks

Handed out 120125 and should be handed in 120208

1

The headlight for a car gives a spot on a (vertical) wall 10 m away that can be described by

where E_v,0= 840 lux and r₀ = 1.2 m.

The center of the illuminated spot is 0.5 m over the ground which is also the headlight distance over the ground.

What is the illumination on the (horisontal) road 50 m in front of the car?

2

The new traffic lights are made from densely packed LED's with a diameter of 3,0mm. In all there are 200 LED's, each giving 0,60lumen, spread ut in a cone with half top angle 6°. What is the luminous intensity och the luminance of the traffic light?

Are both these numbers important for the performance, and if so, in what context are they used?