Lux Level

How are you going to get a streetlight in an office?

I suppose it's possible on the 3^rd floor.

For an office the typical lighting level (illuminance at the desktop due to room lighting) is around 400 lux. For the roadway under a streetlight the level is around 10 lux. In both cases the range is pretty wide.

http://en.wikipedia.org/wiki/Lux

In most cases it is much easier to measure lux level than to try to calculate it. For a simple point lamp in a large room far away from the floor, walls, ceiling or any other reflective surface the illuminance in lux is the number of lumens per square meter and this can be calculated using simple geometry. But in most cases, knowing the output of a lamp in lumens does not tell you the illuminance at a given surface due to complicating factors that include the lamp reflector geometry, the proximity of walls (and their color, surface texture, geometry and orientation) and any other structures in the vicinity of the lamp and surface of interest.

sounds like homework.... as you have internet, then google it! I just did and found loads of stuff... Happy hunting!!

The easiest way to measure the LUX Level is to buy a good light meter. Before automatic exposure became popular everyone carried a light meter.

There are some defined standards for lighting levels however this can be dependent on how the office is going to be used.

In some companies the light levels are kept low to aid the use of computers but in some environments there are defined minimum lighting levels.

Unless you have this information it is rather difficult to answer the question.

Also is the lighting level to be achieved from ceiling lights alone or can task based lighting be used?

Street lighting can vary 100-300 lux

Office lighting is generally 500 lux.

Calculating light you need to take into account the Inverse Square Law, light source intensity, maintenance factors and utilisation factors and distances.

Look into the lumen calculation method.

Calculating light for a street light at certain distances, when you know the height the lamp is mounted at and the distance away you want to calculate you use pythagoras theorem.

Check out the CIBSE Guides, you should find information there.

For seeing the existing Lux level, get a luxmeter.

Standard lux levels are found in handbooks or the net