In an experiment where the independent variable is the material (air, water, or glass) and the dependent variable is the amount of refraction, how do you know the angle of refraction is the outcome (dependent) variable?

What the question is really asking

You are deciding whether the angle of refraction is something you control or something you measure as a result of what you control.

Connecting the variables to the refraction setup

• Test (independent variable): the material the light enters (air, water, glass). This is what you purposely change.
• Outcome (dependent variable): the amount of refraction, meaning how much the light bends when it enters the new material.

A common way to represent “how much it bends” is by measuring the angle of refraction (the angle the refracted ray makes with the normal).

Why the angle of refraction must be the dependent variable

When you switch materials, the light bends differently because the material’s refractive index changes. So the angle of refraction is not set by you, it is the measured response to your choice of material.

Quick check you can use

Ask:

• “Did I choose it?” If yes, it is independent.
• “Did I measure it after changing something else?” If yes, it is dependent.

You choose the material, and you measure the angle of refraction, so the angle of refraction is the outcome variable.