| Date | May 2016 | Marks available | 6 | Reference code | 16M.3.HL.TZ0.8 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 8 | Adapted from | N/A |
Question
Explain how colour in the environment is detected by the eyes and relayed to the brain in humans.
Markscheme
Detected by the cones
OR
Cones are photoreceptors
They are located in the retina/concentrated in the fovea
Three types of cones that absorb different wavelengths of «visible» light
Cones absorb light passing impulse to bipolar cell
Bipolar cells connected to ganglion cells
There is one to one connection of cones to bipolar cells
OR
One to one connection of bipolar cells to ganglion cells
Relayed to the optic nerve
Right field of vision «of both eyes» is sent to the left part of the brain (Vice versa)
Information is passed to the visual cortex/occipital lobe
Examiners report
This question on colour detection was similar to ones that have appeared on past papers and candidates seemed very well prepared for it, with a good number of candidates receiving full marks. Weaker candidates tended to include irrelevant material, such as information on rods, but they were able to get marks for knowing the sequence of transmission of the impulse from the cones to the brain. Few mentioned wavelengths of light.
