An observer looks at a black-and-green striped safety marker while its illumination is increased.
The table shows the responses of two groups of retinal receptor cells.
| Receptor cell group | Minimum light intensity for response / arbitrary units | Detects colour |
|---|---|---|
| T | 6 | No |
| U | 35 | Yes |
The light intensity is increased from 20 arbitrary units to 50 arbitrary units.
Which prediction is correct?
T responds at both intensities and U responds only at 50 units, so the green colour becomes distinguishable.
T and U respond at both intensities, so the green colour is distinguishable at both intensities.
U responds at both intensities and T responds only at 50 units, so the green colour is distinguishable at both intensities.
T responds at both intensities and U responds only at 50 units, so the marker can be seen only at 50 units.
102 exam-style questions on Edexcel GCSE Biology 2.4 The eye, covering 2.4.1 Structure and function of the eye and 2.4.2 Eye defects and their correction. Each one has a worked solution and a mark scheme showing where the marks go.