​The following statements were made about phase contrast microscopy:

A. Phase contrast microscopy can be equally utilized to examine stained and unstained specimens.
B. A phase annulus generates hollow cone of light to illuminate the specimen.
C. A light wave that passes through a cell nucleus and organelles lags compared to the light waves that pass through water only.
D. A polarized light source is used to translate the minor phase shifts into grey values.
E. Appearance of bright halos is a common artifact of phase contrast imaging.

Which one of the following options represents the combination of all correct statements?

Correct option is B

Evaluation of each statement:

A. Phase contrast microscopy can be equally utilized to examine stained and unstained specimens.

• Incorrect.
• Phase contrast microscopy is specifically designed for observing unstained, transparent specimens, like live cells or organelles. Staining is not necessary and may even interfere with phase contrast imaging. Hence, not equally utilized for stained specimens.

B. A phase annulus generates hollow cone of light to illuminate the specimen.

• Correct.
• In phase contrast microscopy, the phase annulus (or ring) in the condenser produces a hollow cone of light, which interacts with the specimen. This is a key part of the optical setup.

C. A light wave that passes through a cell nucleus and organelles lags compared to the light waves that pass through water only.

• Correct.
• This is based on differences in refractive index. Light passing through denser cellular structures (organelles/nucleus) is phase-shifted (delayed) compared to light passing through the surrounding medium (e.g., water or cytoplasm).

D. A polarized light source is used to translate the minor phase shifts into grey values.

• Incorrect.
• Polarized light is used in polarized light microscopy, not in phase contrast microscopy. In phase contrast microscopy, phase rings in the objective lens convert phase differences into intensity differences, not through polarization.

E. Appearance of bright halos is a common artifact of phase contrast imaging.

• Correct.
• Bright halos (halo effect) are a well-known optical artifact in phase contrast images, especially around edges of structures due to interference of diffracted and undiffracted light.

Information Booster:

1. Phase contrast microscopy enhances contrast in transparent, unstained specimens by converting phase shifts into intensity differences.
2. It uses a phase annulus in the condenser and phase plate in the objective lens.
3. It is ideal for studying live cells, organelles, and thin tissues without staining.
4. Phase shifts arise due to variation in refractive index and optical path length.
5. The halo effect is a limitation, but commonly accepted for observing fine structures.
6. This technique avoids phototoxicity and staining artifacts, enabling long-term live imaging.
7. It is widely used in cell biology, microbiology, and developmental studies.