Figuring out the frequency of light using a solar cell

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Hey people,

I wanted to try this experiment. My experiment is to shine a light on a solar cell and try to figure out the frequency of the light. I do have some idea on how to do this using energy concepts.

$$E_i+W_n_c=E_f$$

$$E_i$$= initial energy in the system (joules)

$$W_n_c$$= work that isn't conservative (joules)

$$E_f$$= final energy in the system (joules)

I know that when electricity is passing through a wire it has a voltage and a current. Multiply those two together and you get power. However I can't measure amps directly because doing so will fry the circuit and in particular the solar cell. Current is equal to voltage over the resistance of the circuit so I can substitute that in for amps and still find the power. Multiply by the amount of time to pass and you get watts. I'll show it mathematically below.

$$VI=P$$

$$\frac{V}{R}=I$$

$$\frac{V^2}{R}=P$$

$$\frac{V^2t}{R}=W$$

I know this will be the final energy so it goes on the right side of the equation.

$$E_i+W_n_c=\frac{V^2t}{R}$$

Now the initial energy comes from the light source itself which is represented by

$$h\nu=W$$

so I plug it in.

$$h\nu+W_n_c=\frac{V^2t}{R}$$

However I don't think this equation is complete. I feel that I might be missing something. Can someone help me out?

Thanks!

 

[f95toli]

The only way this experiment could work would be if you were able to use perfectly monochromatic sources with exactly the same intensity.
The problem here is that whereas it is true the energy of a single photon is hf that doesn't tell you anything about how MANY photons are hitting the cell per second; i.e. there is no way to determine the frequency by just measuring the power generated by the cell.

 

[Entropia]

I appreciate your curiosity and interest in conducting this experiment. Your approach of using energy concepts to figure out the frequency of light is a good start. However, there are a few things to consider and clarify in your experiment and equation.

Firstly, the equation you have written is an energy conservation equation, which is used to calculate the change in energy of a system. It is not directly related to frequency. To determine the frequency of light, we need to use the equation E=hf, where E is the energy of a photon, h is Planck's constant, and f is the frequency.

Secondly, when you say "current is equal to voltage over the resistance of the circuit", this is known as Ohm's Law and applies to a complete circuit. In your experiment, the solar cell is not connected to a complete circuit, so Ohm's Law may not be applicable.

Thirdly, the equation you have written assumes that all of the light energy is being converted into electrical energy by the solar cell. In reality, only a fraction of the light energy is converted, and the rest is either reflected or absorbed. This is known as the efficiency of the solar cell, and it varies depending on factors such as the material and design of the solar cell.

To improve your experiment and equation, I suggest considering using a light source with a known frequency, such as a laser, and measuring the output voltage of the solar cell using a voltmeter. You can then use the equation E=hf to calculate the frequency of the light. Additionally, it would be helpful to research the efficiency of your specific solar cell and use that in your calculations. I hope this helps and good luck with your experiment!