Microscopes and magnification Flashcards
What has the development of microscopes allowed us to see more of?
structures of cells
role of sub-cellular structures
When abouts where microscopes invented?
350 years ago
What did the invention of microscopes allow us to see?
cells in organisms
plant, animal and bacterial cells
structures in cells
How do light and electron microscopes magnify objects?
using light
using electrons
What is the greatest possible magnification using light and electron microscopes?
x2000
x10 million
objects in cells can be seen clearer and in more detail
How do you calculate magnification?
magnification (M) = image size (I) / real size (R)
measure image size in mm
multiply by 1000 to get measurement in micrometres
use a scale bar if possible
A cell has a scale bar of 2 micrometres that is 4 cm long. Calculate the magnification.
scale bar = 40 mm
40 x 1000 = 40 000 micrometres
I = 40 000 micrometres
real size (R) = 2 micrometres
M = I / R = 40 000 / 2 M = x20 000
Some cells were viewed by microscope using a x4 eyepiece and a x20 objective. Calculate the magnification of the cells seen througth the microscope.
M of object = M of eyepiece x M of objective
= 4 x 20 = 80
x80
A bacterium is viewed under a light microscope using a x40 objective and a x10 eyepiece. The image is 1.2 mm long. Calculate the actual length of the cell.
M = I / R
M = 40 x 10 = 400 I = 1.2 mm = 1200 micrometres
400 = 1200 / R
1200 / 400 = R = 3
3 micrometres
What is the top part of a microscope called?
eyepiece
What is the larger focusing wheel called?
coarse focusing wheel
What is the smaller focusing wheel called?
fine focusing wheel
What are the lenses called?
objective (or eyepiece)
What is the flat platform called?
stage (with clips)
What is underneath the stage?
mirror or light source
