Practice question

Confocal microscopy achieves optical sectioning and improved contrast by rejecting light originating outside the focal plane. A laser scans point-by-point across the specimen, exciting fluorophores only at focus. Emitted light passes through a small adjustable pinhole placed conjugate to the focal plane, so out-of-focus fluorescence and scattered light are physically blocked before reaching photomultiplier detectors. Serial optical sections can be stacked computationally to reconstruct three-dimensional volumes. This principle dramatically enhances lateral and axial resolution, reduces blur in thick samples, and is essential for immunofluorescence and live-cell imaging of organelles.