Doubly refractile particles are examined using

• A. Polarized light
• B. Brightfield illumination
• C. Darkfield illumination
• D. Phase contrast

Answer: (A)

Doubly refractile means birefringent, so you study these particles with polarized light microscopy. When light enters such a material, it splits into two rays that travel at different speeds along different axes. Using crossed polarizers, the ordinary and extraordinary rays produce interference effects as they exit, giving bright, often color-dependent appearances for the birefringent particles while the surrounding isotropic material stays dark. This setup makes birefringence visible and lets you assess the particle’s orientation and thickness.

Other illumination methods don’t exploit this polarization-based interference. Brightfield shows general absorption contrast, darkfield highlights scattered light, and phase contrast emphasizes phase shifts in light, but none specifically reveal double refraction the way polarized light does.