Light microscopy and phase contrast microscopy: How do they work?

Oh boy.... so my goal was to explain light microscopy and phase contrast microscopy. But I had no idea how complex the theory of phase contrast microscopy was! It is extremely easy to do and use, but the physics of what is going is both brilliant and complex. So in this video I use heuristics. Heuristics are a mental model for something which is simplified but perhaps not technically 100% accurate. Newton's laws of motion are essentially heuristics because they are not100% accurate, they don't take into account the warping of spacetime. But they're an excellent mental model to understand the world. In this video I use heuristics to explain how normal bright-field light microscopy works and how phase-contrast light microscopy works.
Learning objectives
Explain the fundamentals of how a lens works
Describe the main parts of a microscope and what they do
Explain why normal light microscopy (bright-field) has issues when it comes to viewing cells
Describe what constructive and destructive interference is and how they relate to in phase and out of phase waves of light
Explain how phase contrast microscopy works using the notions of constructive and destructive interference and in phase and out of phase waves of light

[@vedwards5027]

Thank you so much for your hard work and research!!!!!

[@kadenjensen8429]

I'm taking microbiology and this helped me understand phase contrast microscopy so much!!!! Thank you for this video!!!

[@chenwang5857]

Great video! Can you explain more why the diffraction light passing through the cell center remains in phase (shown in left diagram)?

[@matiassantacruz5487]

Hi! I have to write a report related to phase contrast imaging. I've been trying to come up with something, but I really don't know what to investigate. Is there anything that comes to mind? Any help would be massively appreciated

[@lotharmayring6063]

but in the PH-objektiv there is a dark phase ring.......