IB Biology IA idea · The human body and exercise

IB Biology IA idea: how visual acuity changes with light level

Your eyes adapt, but only so far. Measure how fine a detail you can resolve as the room darkens.

The human body and exercise
SL ideal
HL good
Lab

By Photon Academy · Updated 13 November 2026

These ideas are starting points, not an IA to copy. Never copy an idea blindly: make the question, method and analysis your own, and check your plan with your teacher.

Example research question

To adapt, never to copy

How does room light level (5, 25, 50, 100, 250 and 500 lux) affect visual acuity (decimal ratio, from the smallest chart line read at 3 m) after 5 minutes of adaptation, in 8 consenting volunteers?

Change the system, the range or the method so the question is yours. Check it against the research question checklist in our Biology IA guide.

Variables

You change: light level in the room, 6 or more values from about 5 to 500 lux, with a dimmer and a light meter
You measure: smallest letter size read correctly at 3 metres, converted to acuity (logMAR or ratio)
You keep the same: same viewing distance and chart
same adaptation time at each level
same volunteers
same glare-free chart illumination

Method

Volunteers wear no tinted lenses and read a printed chart at each light level after 5 minutes of adaptation. Record the smallest line read with at most one mistake.

Data analysis

Mean acuity and standard deviation against log light level, a curve fit, and a Friedman or repeated-measures test across 8 or more volunteers. Uncertainty from chart line steps.

How it works

You change Room light level (lux) and measure Visual acuity (decimal ratio) in Volunteers reading a chart, keeping Viewing distance, Adaptation time, Chart, Corrective lenses the same. Expect a graph of Visual acuity / decimal ratio against Light level / lux: Acuity improves as light rises, then levels off.

Make it yours

Compare rods and cones by testing a dim spot beside a bright one, or add colour filters.

Safety

Take care with: human participants.

Informed written consent from every volunteer (and a parent if under the age your school sets), the right to stop at any time, no invasive procedures, anonymous data, and teacher approval before starting. Do not recruit anyone with a health condition. Do not use bright flashes or lasers; keep rooms safe to move in when dim.

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