Define the following properties of the microscope:a.)magnification b)focal length c)working distance?

a) Magnification : Optical magnification is the ratio between the apparent size of an object (or its size in an image) and its true size, and thus it is a dimensionless number.





Linear magnification — For real images, e.g., images projected on a screen, size means a linear dimension (measured, e.g., in millimeters or inches).


Angular magnification — For optical instruments with an eyepiece, the linear dimension of the image seen in the eyepiece (virtual image in infinite distance) cannot be given, thus size means the angle subtended by the object at the focal point (angular size). Strictly speaking, one should take the tangent of that angle (in practice, this makes a difference only if the angle is larger than a few degrees).





b) Focal Length : The focal length of an optical system is a measure of how strongly it focuses or diverges light. A system with a shorter focal length has greater optical power than one with a long focal length.


http://en.wikipedia.org/wiki/Focal_lengt...





c) Working Distance : Working distance is the distance between the objective lens and the specimen. At low magnification the working distance is relatively long. As you increase the magnification the working distance decreases dramatically. Oil immersion lenses pactically touch the specimen. Be aware of this change in working distance with increasing magnification so as to prevent damage to your specimens.





http://abacus.bates.edu/~ganderso/biolog...

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