6.1 microscopes Flashcards
light microscope
visible light passes through specimen and then through a a glass lens
- the lens bends the light so the specimen is magnified into the eye
ratio of object’s images size to its real size
MAGNIFICATION
resolution
or resolving point
the measure of the clarity of the image
-the minimum distance two points can be separated and still be distinguished as two points
(when we see one star, the telescope may resolve that they are actually two close stars)
light microscope cannot resolve detail finer than
200nm
a small bacterium
contrast
accenuates different parts of a specimen
staining and labeling
who first sees cells
Robert Hooke
-saw dead cells in tree bark
electron microscope
-uses a beam of electrons throughout the specimen or onto its surface
the shorter the wavelength, the _____the
resolution
better
resolution best of election microscopes
.002nm
although cannot resolve things smaller than 2nm
cell ultrastructure
refers to the cellular anatomy revealed by the electron microscope
Scanning electron microscope
detail study
- electron beams scan the surface of sample which usually is coated in thin film of gold
- the beam excites electrons and they are detected by a device that translates pattern of electrons onto a video screen
- 3D image
transmission electron microscope
- studies the internal ultrastructure of cells
- aims beam through thin section of specimen
- specimen is stained with lots of heavy metals which attache to certain cellular structures
- electrons are scattered more in the denser parts
- computer transmits electrons
- electromagnets bed the electron paths to focus on the screen
con of electron microscopy
the way the specimen is prepared,kills it
cytology
the study of cell structure
biochemistry
the study of molecules and chemical processes (metabolism) of cells
