These question are about Optical Spectroscopy. For each question please explain
ID: 885459 • Letter: T
Question
These question are about Optical Spectroscopy. For each question please explain your answer.
1) Why do we need to set the 0% Transmittance on a spectrophotometer? i.e. What are we correcting for?
2) When electromagnetic radiation crosses an interface where the refractive indexes are not equal, the result is which of the following?
a) Refraction b) Dispersion c) Diffraction d) Scattering e. Coherence
3) What is the term used to describe the how close the measured values are to the true value?
a) Sensitivity b) Bias c) Precision d) Resolution e) Resolving Power
4) Give an example of a coherent source _______________________________ and an
incoherent source _______________________________.
Explanation / Answer
1) With no sample tube in the spectrophotometer, the instrument reads 0% transmittance. With no sample in the instrument the light path is blocked, so the photometer reads no light at all that is 0% transmittance. This is the correction for detetctor reading the light passing through our instrument correctly.
2) When electromagnetic radiation crosses an interface where the refractive indexes are not equal, the result is,
a) Refraction
Refraction is simply bending of an incident light when it passes through different medium. Difference in refractive index means different properties of medium which would result in refraction.
3) the term used to describe the how close the measured values are to the true value is,
b) bias
although this terminology is no-longer in use and the most common term used instead is accuracy.
4) Coherent means same type of phases in the photons emitted from a light source and incoherent means diffrent phases of photons emitted from a light source. Thus,
An example of coherent source would be laser light generated using gases such as argon, helium, etc and an incoherent source would be tungsten filament lamp and also LEDs.
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