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1) Which knob on the Spec 20 adjusts wavelength? the wavelength control- is this

ID: 903183 • Letter: 1

Question

1) Which knob on the Spec 20 adjusts wavelength? the wavelength control- is this correct?
Which knob adjusts the value of percent transmittance? the transmittance/absorbance control- is this correct?

2) Describe in words the premise of Beer's Law. Which part of this equation represents the slope of the line? 1) Which knob on the Spec 20 adjusts wavelength? the wavelength control- is this correct?
Which knob adjusts the value of percent transmittance? the transmittance/absorbance control- is this correct?

2) Describe in words the premise of Beer's Law. Which part of this equation represents the slope of the line?
Which knob adjusts the value of percent transmittance? the transmittance/absorbance control- is this correct?

2) Describe in words the premise of Beer's Law. Which part of this equation represents the slope of the line?

Explanation / Answer

1. Yes. wavelength-control adjusts wavelength

The Wavelength Control selects the desired analytical wavelength of the instrument which is indicated on the wavelength scale in the window next to the knob.

Transmittance/absorbance control adjusts the value of percent transmittance.

This control sets the display to 100%T, when a cell containing a blank reference solution is inserted in the sample compartment. It must be reset whenever the analytical wavelength has been changed.

2. Beer's Law: It relates the absorbance of light to the properties of the material through which light is travelling.

If light passes through a cell of path length 'l', containing a sample of concentration 'c', then,

absorbance is given by:

A = l c

When we plot a graph of A vs C, we get a straight line. The slope of the line is the molar absorptivity, .