how to suggests reason for low or high accuracy for different pieces of glasswar
ID: 786968 • Letter: H
Question
how to suggests reason for low or high accuracy for different pieces of glassware
Suggest reasons for the low or high precision for the different pieces of glassware.
Briefly state the advantages and disadvantages for each piece of glassware.
The first column of numbers is experimental volume, then the second is 100mL Beaker third is 50mL graduated Cylinder, fourth is 50mL Buret and final column of numbers is 20mL pipet.
"True" Volumes
100mL 50mL 50mL 20mL
Beaker Graduated Buret Pipet
Cylinder Experimental: 20 20.0 20.00 20.00 Volume
Explanation / Answer
Brightfield microscopy
The microscope that is available to you for general use in this laboratory is a sophisticated optical instrument that can provide you with high-resolution images of a variety of specimens. Image quality is based largely on your ability to use the microscope properly. Below you will find some basic information that you have probably heard before, but information that is rarely presented in a thorough way.
- Resolution -
The magnification of small things is a necessary facet of biological research, but the fine detail in cells and in subcellular components requires that any imaging system be capable of providing spatial information across small distances. Resolution is defined as the ability to distinguish two very small and closely-spaced objects as separate entities. Resolution is best when the distance separating the two tiny objects is small. Resolution is determined by certain physical parameters that include the wavelength of light, and the light-gathering power of the objective and condenser lenses. A simple mathematical equation defines the smallest distance (dmin) separating the two very small objects:
dmin = 1.22 x wavelength / N.A. objective + N.A. condenser
This is the theoretical resolving power of a light microscope. In practice, specimen quality usually limits dmin to something greater than its theoretical lower limit.
N.A. (Numerical Aperture) is a mathematical calculation of the light-gathering capabilities of a lens. The N.A. of each objective lens is inscribed in the metal tube, and ranges from 0.25-1.4. The higher the N.A., the better the light-gathering properties of the lens, and the better the resolution. Higher N.A. values also mean shorter working distances (you have to get the lens closer to the object). N.A. values above 1.0 also indicate that the lens is used with some immersion fluid, such as immersion oil.
From the equation above, you should be aware that the N.A. of the condenser is as important as the N.A. of the objective lens in determining resolution. It is for this reason that closure of the condenser diaphragm results in a loss of resolution. In practice, at full aperture and with good oil immersion lenses (N.A. 1.4 for both the condenser and the objective) it is possible to be able to resolve slightly better than 0.2
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