Lab Exam (Scientific Method/Metric/Microscope)

The factor that is changed or manipulated by the experimenter.

Independent variable

The factor that is measured or observed; it changes in response to the independent variable.

Dependent variable

A testable explanation or prediction about how variables are related.
Example: “If plants get more sunlight, then they will grow taller.”

Hypothesis

A well-supported and widely accepted explanation based on many experiments and observations.

Theory 

Metric system is based on powers of 10.

Prefixes:

• kilo (k) = 1,000

• centi (c) = 0.01

• milli (m) = 0.001
  Example: 1 meter = 100 centimeters = 1,000 millimeters.

Metric conversions

A way to express very large or very small numbers.

Scientific notation

To convert to scientific notation:

Example: 56,000 = 5.6 × 10⁴

move decimal 1 to the right

To convert from scientific notation:

Example: 3.2 × 10⁻³ = 0.0032

Right positive, Left negative

Lens magnifications (4x):

Scanning objective

Lens magnifications (10x):

Low power objective

Lens magnifications (40x):

High power objective

Lens magnifications (100x):

Oil immersion objective

Multiply ocular lens (10×) by the objective lens.
Example: 10× ocular × 40× objective = 400× total magnification

Total magnification calculation

Parts of the microscope -

where you look through

Ocular Lens

Parts of the microscope -

Provide different magnifications

Objective lens

Parts of the microscope -

Holds the slide

Stage

Parts of the microscope - 

Secure the slide 

Stage clips 

Parts of the microscope

Rough focusing 

Coarse focus knob 

Parts of the microscope -

Sharp focusing 

Fine focus knob 

Parts of the microscope -

Controls light amount

Diaphragm

Parts of the microscope -

Provides illumination 

Light source 

Parts of the microscope -

Support the microscope

Arm and Base

How to use a microscope (Step 1): 

Start with lowest power (4×) objective.

How to use a microscope (Step 2): 

Use coarse focus, then fine focus.

How to use a microscope (Step 3): 

Center and focus the image before switching objectives

How to use a microscope (Step 4): 

Always use oil only with 100× lens.

How to use a microscope (Step 5): 

Clean lenses with lens paper only.