Homework Help: Relationship between voltage and distance between source of light from a solar panel

1. Apr 21, 2010

cgi093

I'm conducting a lab in which I change the distance of a lamp from a solar panel and use a multimeter to measure the resulting voltage. What type of relationship am I supposed to find? My results seem to indicate either a relationship with either a quadratic equation as its model or an inverse power equation as its model. Could someone tell me what would make sense here? My class is learning about electricity and circuits, but we haven't yet covered how the concentration of light is dispersed over distance, how that would affect the energy received by a solar panel, etc. Thanks!

2. Apr 21, 2010

cgi093

Re: Relationship between voltage and distance between source of light from a solar pa

Anyone know how this would work?

3. Apr 21, 2010

zachzach

Re: Relationship between voltage and distance between source of light from a solar pa

No, but I naturally would think that the inverse square law of light comes into play somewhere.

4. Apr 21, 2010

cgi093

Re: Relationship between voltage and distance between source of light from a solar pa

Thanks, but since we haven't gone into any more detail with light than diffraction and refraction and stuff like that, I can't really use that too much. Thanks for the input though.

Anyone else?

5. Apr 21, 2010

zachzach

Re: Relationship between voltage and distance between source of light from a solar pa

Well maybe you should learn. The inverse square law for light is a very fundamental one and certainly plays into your problem. I personally think it is the only thing that plays into your problem along with how the voltage changes with respect to how much power the panel is receiving. http://hyperphysics.phy-astr.gsu.edu/hbase/vision/isql.html.

6. Apr 21, 2010

Hellabyte

Re: Relationship between voltage and distance between source of light from a solar pa

Well I would guess that you would see the voltage across the panel drop as basically something like

$$V \propto \frac{1}{r^2}$$

Think about the radiation from one really tiny amount of time let out from your light bulb. It will leave and propagate in all different directions equally creating a spherical shell of radiation. At further distances away from the bulb this spherical shell will be large and have a large surface area. However the same amount of energy will be stored in the light in that area. Because the surface area of a sphere is $$4\pi r^2$$ our power will get spread out as one over this or $$\propto 1/r^2$$.

Here is the wikipedia article on the basic principle behind this, it shows up everywhere. and the picure is a good demonstration of what i was saying to visualize.

http://en.wikipedia.org/wiki/Inverse-square_law

7. Apr 21, 2010

cgi093

Re: Relationship between voltage and distance between source of light from a solar pa

Okay thanks a lot guys. I think this will definitely get me started.