# What is the relationship of this formula?

1. Apr 17, 2013

### Outrageous

E(lux), I (candelas) , r(meters)
E=I/r^2.

What is this formula ? I got it from a photovoltaic cell experiment. Use solar cell connect to a micro ammeter to detect the current produced due to the intensity of the light source.
The bigger the r , the lower the current.
how does the formula relate to current??

2. Apr 18, 2013

### counterphit

Basically that is a representation of the inverse square law of EM propagation. Each doubling of your distance from source equates to a four fold decrease in intensity.

3. Apr 18, 2013

### Outrageous

In the photovoltaic cell experiment , the E is luminance or normal illuminance which is directly proportional to the current produced by the photovoltaic cell?

Is that possible to use the same set up to detect the illuminance by having same changes to the micro ammeter used? I mean when the cell is not normal to the light source, then the current gained is not same as the current gained when the cell is normal to the light source. My question is no matter the cell surface move with any angle, is that possible to get the reading of current which is directly proportional to the illuminance by doing something to the micro ammeter

Thank you so much

Last edited: Apr 18, 2013