Importance of Angle in Light Spectrometry for Reflectance Measurements

In summary, the conversation revolved around using a light spectrometer to measure the reflectance of a protein sample on a glass slide. The original intensity was too high, so the user used an aperture to reduce it. However, the percent transmission was still very high, leading to confusion and questions about the relevance of the angle of the slide and the accuracy of the measurement. The high transmission value was calculated by the software using input from the spectrometer.
  • #1
Rafimah
12
1

Homework Statement


Hello,

I've been using a light spectrometer to try to measure the reflectance of a sample of a protein I have on a glass slide. I followed the manual's instructions and first took a dark spectrum and a reference spectrum. However, the intensity was too high (far above the maximum recorded value of 4095 counts), so I used an aperture to reduce the amount of light released by the lamp I was using. This worked well, as for the reference spectrum I needed a peak at 3500 counts. However, when I looked at thee percent transmission, I noticed it was incredibly high (around 1000%). I placed a sample in there, just to test if that would improve anything, but it did not. Does anyone have experience with this and measuring the reflectance of samples?

The Attempt at a Solution


I thought that the angle of the slide might be relevant. Does anyone know how important the angle is in light spectrometry? Unfortunately, the sample is placed in a holder and, while the slide can touch anything, the sample itself cannot be contaminated, so I was forced to place it at a roughly 45 degree angle.
 
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  • #2
1000% transmission doesn't make sense, you cannot transmit more than all light (100%). How did you get that value?
 
  • #3
That was the main problem. I was using a USB2000+ spectrometer to measure the transmission of light that was coming through a fiber optic cable. I'm not sure why the transmission is so high.
 
  • #4
Where does the number come from? DId you calculate it? Did some software calculate it based on input values (based on what)?
It is hard to spot the problem if you don't explain what exactly you did.
 
  • #5
The number was calculated by the software based on the input from the USB2000+.
 

What is percent transmission and why is it important in scientific research?

Percent transmission is a measure of the amount of light that passes through a sample compared to the amount of light that is incident on the sample. It is important in scientific research as it allows us to quantify the amount of light absorbed or transmitted by a sample, which can provide valuable information about the properties of the sample.

What is error in percent transmission and how is it calculated?

Error in percent transmission is the difference between the measured percent transmission and the true percent transmission. It is calculated by taking the absolute value of the difference between the measured and true percent transmission values, divided by the true percent transmission, and multiplied by 100 to get a percentage value.

What factors can contribute to errors in percent transmission?

There are several factors that can contribute to errors in percent transmission, including variations in the intensity of the incident light, imperfections in the sample or sample holder, and errors in the measurement equipment. Other factors such as temperature, humidity, and sample preparation techniques can also affect the accuracy of percent transmission measurements.

How can errors in percent transmission be minimized?

To minimize errors in percent transmission, it is important to calibrate the measurement equipment regularly, use high-quality samples and sample holders, and take multiple measurements to account for any variations. Other ways to minimize errors include controlling environmental factors, using proper sample preparation techniques, and carefully following measurement protocols.

Why is it important to report errors in percent transmission in scientific studies?

Reporting errors in percent transmission is important in scientific studies because it provides a measure of the accuracy and reliability of the data. It allows other researchers to understand the potential sources of error and evaluate the validity of the results. Additionally, reporting errors allows for better comparison and reproducibility of results between different studies.

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