BBC Knowledge April 2017

CORBIS

Eye candy

ZHENGZHOU PROVINCE,

CHINA

Motorists driving through the outskirts

of Zhengzhou, China, may find

themselves dazzled by a flashy new

addition: a motorway tunnel that’s

as bright as a bag of Skittles.

The 400m underpass opened in

January and features multicoloured stripes

throughout. While there is no doubt that

it looks incredible, the spectrum of colours

serves a serious scientific purpose:

it helps drivers’ eyes adjust to the changing

light as they enter and exit the tunnel.

“Our eyes are better at seeing bluer

colours in dim light,” explains Ananth

Viswanathan, consultant ophthalmologist

at Moorfields Eye Hospital, Dubai, UAE.

“This is because our eyes have two main

types of light-sensitive cells – cones

for bright light and rods for dim light.

The cone system is better at longer red

wavelengths, whereas the rod system is

better at shorter blue wavelengths.

“Having bluer colours in the central

dimmer section of the tunnel makes sense

as colour vision changes at different light

levels,” he adds.

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48 April 2017

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40 April 2017