> See also: > - [[Microscopy]] # Optical Microscopes ## Properties of Optical Microscopes There are three major properties associated with microscopes: 1. *Illumination* 2. *Magnification* 3. *Resolution* ### Magnification Power Using a microscope isn't useful unless you know the **power of magnification** being used. Without it, you would have no reference for the scale of what was being observed. When looking through a compound light microscope, the image is actually *magnified twice* by two different components of the microscope: 1. The *objective* provides the primary magnification 2. The image is also magnified 10 times by the *oculars*, themselves. ### Diffraction Limits - the ability to differentiate two separate objects vs a blurred together combination - resolvable vs unresolvable *When using 100X objectives, an oil immersion is required.* When light passes through objects, such as the glass slide with the sample being studied, it will refract, or bend, and some of the light will be lost in the process. Because oil has the same refractive index as glass it can stop the refraction of light between the specimen and the lens allowing for better resolution overall. - The objective lens should be touching the oil for this to succeed ### Resolution Resolution is how small something can be where it can still be identified as its own entity. In microscopy, a lower resolution is better as Resolution is expressed as $d$. $d=\lambda/(2NA)$ - $d$ = *Resolution* - $\lambda$ = *Wavelength of Light* (Illumination (nm)) - $NA$ = *Numerical Aperature* (Light gathering capacity of the lens) ## Compound Microscopes ![[Pasted image 20220802185811.png|400]] | Part | Function | | --- | --- | | Ocular | Part of the microscope the viewer looks through | | Objective | Switching between these allows for a more magnified view | | Course Focus | Useful for making large-scale adjustments to the image | | Fine Focus | Useful for making small-scale adjustments to the image | | Lightbulb | Illuminates the object so that it can be viewed through the microscope | | Stage | Holds the slide and can be moved to adjust the position of the image |