Chapter 1: Cell Structure
Sunday, 24 April 2022 2:52 PM
MICROSCOPY:
Magnification: The number of times an image is larger compared to the real size of the object
Magnification = image size / actual size
Total magnification = eyepiece lens magnification x objective lens magnification
Eyepiece graticule & Stage micrometer: used to measure the size of the object when viewed under microscope
• Stage micrometer has 3 lines each 10 μm apart
• 40 graticule divisions = 10 μm
• 1 graticule division = 10/40 = 0.25 μm
• Measurement = graticule divisions x
magnification factor
Resolution: ability to distinguish between 2 separate points
Resolution of electron microscope = 0.5 nm
Resolution of light microscope = 200 nm (half the smallest wavelength of visible light, 400 nm)
LIGHT MICROSCOPE ELECTRON MICROSCOPE
Light as a source of radiation Electrons as a source of radiation
400 nm - 700 nm wavelength of radiation 0.005 nm wavelength of radiation
Max resolution = 200 nm Max resolution = 0.5 nm
Specimen: living / dead Specimen: dead
Stains: coloured dyes Stains: heavy metal atoms
Natural colour of specimen maintained All images in black and white
Cheap to purchase and operate Expensive
Small and portable Large and requires 0[special rooms
Simple and easy sample preparation Lengthy and complex sample preparation
Vacuum not required Vacuum required
AS BIOLOGY NOTES Page 1
Sunday, 24 April 2022 2:52 PM
MICROSCOPY:
Magnification: The number of times an image is larger compared to the real size of the object
Magnification = image size / actual size
Total magnification = eyepiece lens magnification x objective lens magnification
Eyepiece graticule & Stage micrometer: used to measure the size of the object when viewed under microscope
• Stage micrometer has 3 lines each 10 μm apart
• 40 graticule divisions = 10 μm
• 1 graticule division = 10/40 = 0.25 μm
• Measurement = graticule divisions x
magnification factor
Resolution: ability to distinguish between 2 separate points
Resolution of electron microscope = 0.5 nm
Resolution of light microscope = 200 nm (half the smallest wavelength of visible light, 400 nm)
LIGHT MICROSCOPE ELECTRON MICROSCOPE
Light as a source of radiation Electrons as a source of radiation
400 nm - 700 nm wavelength of radiation 0.005 nm wavelength of radiation
Max resolution = 200 nm Max resolution = 0.5 nm
Specimen: living / dead Specimen: dead
Stains: coloured dyes Stains: heavy metal atoms
Natural colour of specimen maintained All images in black and white
Cheap to purchase and operate Expensive
Small and portable Large and requires 0[special rooms
Simple and easy sample preparation Lengthy and complex sample preparation
Vacuum not required Vacuum required
AS BIOLOGY NOTES Page 1
