Light Sensitive Devices

[Taksehasam]

Summary:: Need help with LDR's, experiments/ investigations

I need to do an Investigation on Light Sensitive Devices, what 3 experiments could I do with similar aims that are somehow related, also does anyone know how different filters on light - frequency changes affect LDR's or where I could find more information on this?

 

[Charles Link]

See post 2 of https://www.physicsforums.com/threads/photodiode-for-light-detection.924013/#post-5832683
For experiments, demonstrating linear response by using a couple of identical sources, and/or scaling with the inverse square law with distance can be a good thing to show.

 

[berkeman]

Summary:: Need help with LDR's, experiments/ investigations

I need to do an Investigation on Light Sensitive Devices, what 3 experiments could I do with similar aims that are somehow related, also does anyone know how different filters on light - frequency changes affect LDR's or where I could find more information on this?

Welcome to the PF.

We need you to show your efforts on your homework question before we can offer much tutorial help. What are your thoughts so far?

Also, is a human pupil considered a "light sensitive device" for this assignment?

 

[Taksehasam]

Welcome to the PF.

We need you to show your efforts on your homework question before we can offer much tutorial help. What are your thoughts so far?

Also, is a human pupil considered a "light sensitive device" for this assignment?

This isn't a homework question it's my Investigation for Advanced Higher Physics, little help is given by the teacher in regard to the aim and how to do the experiment. I was considering doing light filters with a Light Sensitive Devices for one experiment. The other two I'm not sure yet but I've thought about doing a simple light intensity and distance away frkm the Device. What kind of Light Sensitive Devices could I compare in these and what convulsions would be drawn? I also got a hint regarding the frequency of the light and how fast the device reacts to different frequencies as something I should do in the Investigation.Any other ideas are welcome.

Sorry for posting in the wrong place, it's my first post :)

P.s a human eye would not be considered a Light Sensitive Device

 

[Charles Link]

I also got a hint regarding the frequency of the light and how fast the device reacts to different frequencies as something I should do in the Investigation.

The electronic frequency response is generally wavelength independent, and can be measured by modulating the incident light with a high speed chopper or other device. The wavelength response is found alternatively by seeing how the device responds to light of different wavelengths. This experiment requires optical filters and also a power meter with a flat spectral response that can measure the input power. Suggest you begin with something simpler than these two experiments. Building an op-amp photocurrent amplifier would be a good starting point.
Suggestion @berkeman would be to move this thread to the DIY section. It is a lot different than a typical homework problem.

 

[Charles Link]

See https://en.wikipedia.org/wiki/Photodiode
If you look at the I-V curve in this "link", you can see you get a linear response if you measure the photocurrent at or near zero voltage, as opposed to measuring the output voltage of the device. The op-amp current amplifier circuit is ideal for this purpose.
To give you a little background info, individual photodiodes should still be commercially available that have areas nearly 1.0 cm^2. In many cases, they are now also manufacturing focal plane arrays for cell phone cameras etc. where they may put more than a million pixels inside an area of 1.0 cm^2. I think you would do well to work with a single photodiode before experimenting with focal plane arrays.