Optical microscopes

• What does an optical (light) microscope use to form an image?

  Light
• What is the maximum resolution of an optical microscope?

  0.2 micrometres (μm)
• Which organelles cannot be seen with an optical microscope?

  Ribosomes, endoplasmic reticulum, lysosomes
• Can mitochondria be seen clearly with an optical microscope?

  No, mitochondria are not clearly visible
• What organelle can definitely be seen using an optical microscope?

  The nucleus
• What is the maximum useful magnification of an optical microscope?

  x1500
• What is the first step in preparing a temporary mount of a specimen on a slide?

  Pipette a drop of water onto the slide and place the specimen
• Why is a stain added to a specimen?

  To make objects visible and easy to identify in the cell by increasing contrast
• How do you add a cover slip when preparing a temporary mount?

  Tilt and lower the slip to avoid air bubbles
• What is the purpose of a cover slip?

  To protect the specimen
• What does magnification refer to?

  How much bigger the image is compared to the specimen
• What is the formula for magnification?

  Magnification = size of image ÷ size of real object
• How do you calculate actual size?

  Actual size = image size ÷ magnification
• What should you do if the size of the image and the actual size have different units?


  Convert them to the same units
• What does resolution refer to in microscopy?

  The ability to distinguish two objects as separate
• What tool is used to measure cell size under a microscope?

  Eyepiece graticule
• What is the eyepiece graticule?

  A scale ruler on the eyepiece lens
• How do you calibrate the eyepiece graticule?

  Using a stage micrometer
• What is a stage micrometer?

  A precise measuring scale on the microscope stage
• How do you calculate the distance of one division on the eyepiece graticule?

  Count divisions on the graticule corresponding to a measurement on the micrometer
• What is the relationship between milimeters and micrometers ?

  1 mm = 1000 μm