# Help me design an optics experiment!

**URL:** <https://boards.straightdope.com/t/help-me-design-an-optics-experiment/190713>\
**Category:** Factual Questions\
**Created:** [July 24, 2003, 8:37pm UTC](https://boards.straightdope.com/t/help-me-design-an-optics-experiment/190713 "2003-07-24T20:37:48Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![cj\_finn](https://avatars.discourse-cdn.com/v4/letter/c/4bbf92/32.png) [@cj\_finn](https://boards.straightdope.com/u/cj_finn)\
**Post date:** [July 24, 2003, 8:37pm UTC](https://boards.straightdope.com/t/help-me-design-an-optics-experiment/190713/1 "2003-07-24T20:37:48Z")

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I need to determine the reflectance of a particular fabric with respect to visible light and infrared light. I have on hand a light source that emits 95% of its light intensity in the range of 425 and 475 nm and a digital radiometer that measures the intensity of light in the range of 420-480 nm. I also have a chocolate bar and a can opener Mr. MacGyver, so go to it.

Seriously though, I’m imagining that I could lay down a piece of fabric and emplace the radiometer behind a shade such that the only light incident upon the radiometer would be reflected and then calculate the ratio of incident light to reflected light. But what am I gonna do about the infrared? Can I use an IR thermometer to obtain results that I wouldn’t be embarassed about? Anybody know of a cheap IR detector that would suffice? Or at least know where I could go to borrow/rent/hire one in the Twin Cities?

Your assistance would be very welcome.

Regards,

CJ