Exercise 1: Microscope

• Objects that are one-tenths of a millimeter cannot be seen with the naked eye.
• Light microscopy - uses light to illuminate specimens and create images where the specimen is dark and set against a bright background
• Compound light microscopes - make use of a two-lens system to obtain images of thin minute specimens such as tissue sections and blood smears.
• Specimen - macroscopic specimen larger than 5 cm in length
• Pillar - vertical extension of the base
• Upper parts of the microscope rest on the arm
• Arm is connected to the pillar via an inclination joint
• Stage - base the of arm
• What two lens systems controls the sharpness and size of the image of a specimen?

  Ocular

  Objective lens
• Ocular(eyepiece) - Where you view the specimen and its magnification
• Two or more objectives are attached to a revolving nosepiece at the base of the body tube
• What are the four main types of objective lens and their respective magnification from lowest to highest?

  Scanning objective (4x), Low-power objective (10x), High-power objective (40x), Oil-immersion objective (100x)
• Coarse/fine adjustment knobs - move either the body tube or stage at greater and smaller intervals respectively
• The quality of light used by the microscope depends on parts below the stage (substage)
• Mirror - attached to the pillar
• What are the two reflecting surfaces of a movable mirror in a microscope?

  plane

  concave
• What are the components of the substage?

  condenser

  iris diaphragm
• Condenser - focuses light unto the specimen
• Iris diaphragm - below the condenser and adjusting the lever regulates amount of light passing through the condenser
• The lenses of the microscope produce enlarged images of specimens, a process called magnification
• Resolution - the ability of the microscope to distinguish two points of an image
• Linear magnification - relative size of the final image seen by the eye to the object after light passes through the objective and ocular
• Numerical aperture - a number between 0 and 1 that denotes the resolving power of an objective.
• Oil immersion objective - If NA values are greater than 1, then a special medium for light to travel is required
• Field of view - area of the specimen observable
• Contrast - The difference in brightness between two areas of the same color or the ability to distinguish the details of the specimen as compared to the background
• What part of the microscope can be used to adjust the contrast of the image?

  Iris Diaphragm
• Parfocal microscope - A microscope in which the focus is maintained even when the objective is changed
• Parcentered microscope - one in which the object in the center of view will remain in the center when the objective is rotated
• eyepiece micrometer - quantities such as length, diameter, and distanced can be measured which possesses a graduated scale with no inherent value
• What is the value of each division in the eyepiece micrometer dependent on?

  ocular used

  objective used
• Stage micrometer - slide provided with a scale with known values, usually in tenths or hundredths of a millimeter.
• Can you label the parts of the microscope from 1 to 18?

  1. Eyepiece
  2. Draw Tube
  3. Revolving nosepiece
  4. Body tube
  5. High power objective
  6. low power objective
  7. Coarse Adjustment knob
  8. Fine adjustment knob
  9. Arm
  10. Stage Clips
  11. Stage
  12. Inclination Joint
  13. Pillar
  14. Substage knob
  15. Condenser
  16. Iris Diaphragm
  17. Mirror
  18. Base

  
• Xylene - recommended when removing thick gummy substances such as immersion oil or hydrophobic stains
• Real image - The image formed by a convex lens on a plane mirror.
• Virtual image - caused by plane mirrors, convex mirrors and concave lenses