Week 10: Post lab Questions – Environmental Solutions I (25 points)

Scientists use an instrument called a spectrometer to quantitatively determine the amount of light absorbed by a solution. The primary inner parts of a typical spectrometer are described below. The spectrometer has a light source that emits white light containing a vast mixture of different wavelengths of electromagnetic radiation. The wavelength of interest is then selected using a monochromator (“mono” meaning one and “chromate” meaning color) and an additional exit slit. The separation of white light into different colors (wavelengths) is known as diffraction. The selected light then reaches the sample and depending on how the light interacts with the chemical compound of interest, some of the light is absorbed and some passes straight through. By comparing the amount of light entering the sample (P0) with the amount of light reaching the detector (P), the spectrometer is able to tell how much light is absorbed by the sample.

Define all of the bold words in the previous paragraph. (4 points)

Spectrometer: an optical instrument that can detect spectral lines. It measures it’s wavelength and intensity.

Quantitatively: something that is part of the metric system, can be given a numerical value.

Electromagnetic radiation: radiation that includes radio waves, visible light, x-rays and gamma rays, where the magnetic and electric fields vary at the same time.

Monochromator: an optical instrument that transmits a mechanically selectable narrow band of wavelengths of light or other radiation which is chosen from a wider range of wavelengths that are available at the input.

Diffraction: a process where a beam of light or another system of waves is spread out because they pass through a narrow aperture or across an edge. Usually accompanied by interference between