Immersion Oil

 Type A immersion oil has a refractive index of 1.5150 at the sodium D‑line (589 nm) and a relatively low viscosity of approximately 150 cSt at 23 °C. It’s a general-purpose oil, ideal for reducing air bubble entrapment, making it especially suitable for beginners and routine bright-field microscopy. 

 Type B features the same refractive index (1.5150 at 589 nm, 23 °C) but with a much higher viscosity of about 1250 cSt, offering thicker coverage. This makes it perfect for batch processing or examining multiple slides without needing reapplication, improving workflow efficiency. It’s a general-purpose, cost-effective choice.