LAB 1: The Microscope

• The ocular lens (eyepiece) serves what purpose?

  They magnify the image from the objective lens.
• What is a parfocal lens system?

  A lens that maintains its focus as you change from one objective lens to another.
• What is Methylene Blue used for in this lab?

  To stain cell components
• Resolution is the ability to distinguish two objects that are close together.
• Contrast is the ability to distinguish an object from its background.
• The head holds the eyepieces.
• The nosepiece holds the objective lens.
• What is the function of objective lens?

  To magnify the image and increase resolution
• The frame (stand) holds the parts of the microscope in position.
• Coaxial Coarse and Fine Focus Adjustment Knob:

  • Moves the stage up or down to adjust the focus of the image of the specimen.
• • Coarse Adjustment: The large part at the base changes focus relatively rapidly.
  • Fine Adjustment: The small part at the tip changes focus relatively slowly and is typically used to bring an image into sharp focus.
• When do you use the coarse adjustment knob?

  The coarse adjustment knob should only be used with the scanner or low power objective lens.
• When do you use the fine adjustment knob?

  To focus on the specimen at high magnification
• What is the stage on a microscope?

  A platform on which the specimen is placed.
• The stage clip holds slide in place on stage.
• Coaxial Stage Motion Knob:

  • Moves the slide held by the stage clip.
  • The large part at the base moves the slide towards or away from the stand. The smaller part at the tip moves the slide right or left.
• What is the function of the condenser?

  Focuses light from lamp onto the specimen
• Condenser:

  • Focuses light from the lamp onto the specimen.
  • There is an adjustment knob to move it up or down.
  • It includes the aperture iris diaphragm.
• The aperture iris diaphragm controls the angle of light reaching the specimen, and thus adjusts contrast.
• What is the condenser held by?

  The condenser is held in place by centring screws used to centre the condenser.
• Lamp:

  • Provides light to illuminate specimen, there is an on/off switch.
  • Brightness may be adjusted with the lamp intensity knob.
  • It includes the field iris diaphragm.
• The field iris diaphragm controls the width of the beam of light reaching the condenser, and so adjusts contrast.
• The working distance is the distance from the objective lens to the specimen when the specimen is in focus.
• What is depth of focus?

  The thickness of the region in which the image is sharply in focus
• What does the depth of focus depend on?

  The magnification of the objective lens: the higher the magnification, the narrower the depth of focus.
• Magnification is the apparent increase in the size of the specimen.
• • If the objective lens is too close or too far from the specimen, the image will be out of focus.
• What advantage does staining provide?

  The staining sticks to molecules in the cells and increases contrast.
• What is the disadvantage of staining?

  The staining is toxic to the cell.
• What is a disadvantage of the dissecting microscope?

  You can not able to view images at high magnification.
• What is an advantage of the dissecting microscope?

  They produce clear 3D images of samples.
• Which objective lens on this microscope has the greatest depth of focus?

  10x
• Which objective lens has the smallest working distance?

  40x
• What is the difference between magnification and resolution?

  Magnification increases an image. Resolution is the ability to see two dots that are really close together.