optical sensor questions. a) Optical sensor normally consist of optical detector

Question

optical sensor questions.

a) Optical sensor normally consist of optical detector and light emitter. Name Two (2) types of optical detector and light emitter b) Provide THREE (3) advantages of photodiode array (PDA) over charge couple device (CCD) c) Electromagnetic light spectrum has a few light bands. Name THREE (3) of them that are normally used as a light source for a sensor system d) The Beer-Lambert law is the linear relationship between absorbance and concentration of an absorbing medium, However it has some limitations. List THREE (3) of them e) Draw a schematic diagram of a spectrometer and label the main components

Explanation / Answer

a). 1. LED (Light Emitting Diode)

2. LASER (Light Amplification by Stimulated Emission Radiation)

b). The advantages of Photodiode are:

1) High Signal to Noise Ratio: A longer integration time allows a higher S/N since the signal will be larger and noise averaged more completely towards zero.

2). Wavelength Precision: a photodiode array UVVis spectrophotometer acquires data at each wavelength by electrical scanning. In this way, the wavelength reproducibility of a PDA instrument is much better than the conventional mechanical scanning UV-Vis spectrophotometer.

3). Minimal stray light effects.

c). The main bands used, in order of decreasing wavelength (hence increasing frequency and photon energy) are:

d). The chemical and instrumental factors that limits the linearity of the Beer-Lambert law are as follows:

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