Lab 1: Microscopes

Question 1

Occular lens

Both

Answer 1

Lens located inside eyepiece that is used to magnify specimen

Question 2

Objective lens

Both

Answer 2

Lens located on the nosepiece above the stage that maginify the specimen.

Question 3

Arm

Both

Answer 3

Used for hand grip while carrying instrument

Question 4

Coarse focus knob

Both

Answer 4

Roughly focuses specimen by changing the distance between objective lens and specimen.

Question 5

Light source

Both

Answer 5

Emits light onto specimen

Question 6

Blue filter

Both

Answer 6

Increases resolution by reducing wavelength of light.

Question 7

Mechanical stage and mechanical stage knobs

Compound

Answer 7

• Supports the slide/specimen over the hole that admits light from below.
• Moves slide around the stage surface.

Question 8

Fine focus knob

Compound

Answer 8

Sharply focuses specimen by precisely changing the distance between the obj lens and specimen.

Question 9

Condenser and condenser adjustment knob

Compound

Answer 9

• Contains 2 lens that focus light onto specimen.
• Moves condenser up or down.

Question 10

Iris diaphragm and iris diaphragm lever

Compound

Answer 10

• Regulates amt of light passing through condenser.
• Opens and closes iris diaphragm.

Question 11

Lamp switch and lamp intensity dial

Compound

Answer 11

• Turns light on or off.
• Adusts light produced by light source.

Question 12

Stage

Dissecting

Answer 12

Supports slide/specimen over the hole that admits light from below.

Question 13

Main switch

Dissecting

Answer 13

Controls supply of power to microscope. Must be “on” for either light to work.

Question 14

I switch and T switch

Dissecting

Answer 14

• Turns light above specimen on/off.
• Turns light below specimen on/off.

Question 15

Stage clips

Dissecting

Answer 15

Holds a slide in position over the stage.

Question 16

What to consider when choosing which microscope to use

Answer 16

1. Size of specimen
2. Whether specimen is dead or alive.
3. Whether you want to see internal or external detail.

Question 17

Types of specimens seen by compound microscopes. Give examples

Answer 17

1. Small and transparent
2. Living or dead
3. Internal details

E.g. unicellular organisms

Question 18

Types of specimens seen by dissecting microscopes. Give examples

Answer 18

1. Large and generally not transparent
2. Living or dead
3. External details

E.g. insects and flowers parts.

Question 19

Types of specimens seen by transmission electron microscopes. Give examples

Answer 19

1. Small
2. Dead
3. Internal details

E.g. viruses and smaller organelles.

Question 20

Types of specimens seen by scanning electron microscopes. Give examples

Answer 20

1. Small
2. Dead
3. External details

Question 21

Similarities between TEM and compound microscopes

Answer 21

Can both see internal details.

Question 22

Similarities between dissecting microscopes and compound microscopes

Answer 22

Can both see living or preserved (dead) specimen.

Question 23

What is field of view? How do you estimate actual size of specimen?

Answer 23

1. Area that can be seen in the circle of light when looking thru the microscope.
2. Fraction of field diameter occupied x field diameter.

Question 24

Resolution

Answer 24

The minimum distance between 2 points that can be separated and still be distinguished as separate units.

Question 25

Depth of field

Answer 25

The vertical distance that remains in focus at one time.

Question 26

Contrast

Answer 26

Ability to discern detail in a light micorscope image against the background.

Question 27

Parfocal lens

Answer 27

Lens that stay in focus when magnification is changed.

Question 28

How to improve the contrast

Answer 28

1. Add a stain to the specimen. 2. Adjust light intensity dial or iris diaphragm. 3. Adjust the condenser.

Question 29

What is the relationship between magnification and depth of field?

Answer 29

Negative/indirect relationship.

Question 30

Magnification. Formula for magnification of a drawing.

Answer 30

1. Ability to see details that you wouldn't be able to see with the naked eye. 1. Mag. = size of drawing divided by actual size (units have to be the same).

Question 31

Compound microscope: magnification of objective lens and field diameter (mm)

Answer 31

Low power: 4x, 4.8 mm. Medium power: 10x, 1.8 mm. High power: 40x, 0.5 mm. Oil immersion: 100x. ## Footnote total mag. = occular lens x objective lens

Question 32

Dissecting microsope: magnification of objective lens and field diameter (mm)

Answer 32

Low power: 2x, 9 mm. High power: 4x, 5 mm.