Question 1

A light-beam chopper in a double-beam-in-time spectrophotometer is used to:

Accepted Answer

A light-beam chopper in a double-beam-in-time spectrophotometer is used to compensate for light source variation by alternately blocking and passing light through the sample and reference cells, thereby eliminating any variations in the light source intensity. It is not used to isolate light of a desired wavelength, atomize a sample, or provide polarized light.

Question 2

The visible spectrum is composed of those wavelengths between 380 and 750 nm.

Accepted Answer

This is correct according to the typical definition of the visible spectrum, which includes the colors of the rainbow (red, orange, yellow, green, blue, indigo, and violet) and ranges from approximately 380 to 750 nanometers (nm) in wavelength.

Question 3

Which two optical techniques are combined operationally in a flow cytometer?

Accepted Answer

A flow cytometer uses laser-induced fluorometry to identify fluorophores on individual cells, and light scattering techniques to measure cell size and shape. This combination allows for rapid, accurate analysis of large populations of cells in a fluid stream. Option B is incorrect because atomic absorption spectrophotometry is not used in flow cytometry. Option C is also incorrect because spectrophotometry measures the absorbance of light by a sample, and fluorescence polarization measures the orientation and rotational mobility of fluorophores. Option D is incorrect because fluorescence polarization is not used in flow cytometry.

Question 4

In a fluorometric measurement,the difference between the maximum wavelength of the excitation light and the maximum wavelength of the emitted fluorescence light is a constant referred to as:

Accepted Answer

The constant difference between the maximum wavelength of the excitation light and the maximum wavelength of the emitted fluorescence light is called the Stokes shift. This shift occurs due to the relaxation of energy during the excitation-emission process, and is an important characteristic used in fluorometric measurements. The other options (A, B, and C) do not accurately describe this phenomenon.

Question 5

Which one of the following optical techniques is not considered an emission technique?

Accepted Answer

Nephelometry is not considered an emission technique, but rather a scattering technique that measures the amount of light scattered by particles in a sample. Phosphorimetry, luminometry, and fluorometry all measure emitted light, either from a phosphorescent material (phosphorimetry), a chemical reaction (luminometry), or fluorescent molecules (fluorometry).

Quiz 9: Optical Techniques

A light-beam chopper in a double-beam-in-time spectrophotometer is used to:

The visible spectrum is composed of those wavelengths between 380 and 750 nm.

Which two optical techniques are combined operationally in a flow cytometer?

In a fluorometric measurement,the difference between the maximum wavelength of the excitation light and the maximum wavelength of the emitted fluorescence light is a constant referred to as:

Which one of the following optical techniques is not considered an emission technique?