American Society for Clinical Pathology (ASCP) Technologist in Cytogenetics certification (ASCP CG) Practice Test

In fluorescent microscopy, the exciter and barrier filters used depend on what factor?

1. Type of microscope used

2. Wavelength of light used

3. Stain, as the wavelength for emission can vary

4. Type of sample being analyzed

The correct answer is: Stain, as the wavelength for emission can vary

In fluorescent microscopy, the exciter and barrier filters are crucial components that ensure the correct wavelengths of light are used to excite the fluorophores in a sample and to filter the emitted light before it reaches the detector. The choice of filters is predominantly influenced by the specific fluorophore being used in the staining process since each fluorophore has unique excitation and emission wavelengths. When a sample is stained with a particular fluorophore, it will emit light at a specific wavelength when excited by a particular wavelength of light. Therefore, the exciter filter must be suited to allow the light that excites this specific fluorophore to pass through. Simultaneously, the barrier filter needs to allow the emitted light to pass while blocking any excitation light and any other wavelengths that are not associated with the fluorophore's emission spectrum. This reliance on the characteristics of the stain for selecting the appropriate wavelengths for filtering makes it clear that the choice of exciter and barrier filters specifically depends on the stain and its associated emission wavelengths, making this the correct answer.