Q 01/05

Which optical effect, named for a British physicist, makes the daytime sky and the deep sea look blue?

A) Refraction

B) Total internal reflection

C) The Doppler effect

D) Rayleigh scattering

Answer · why

D) Rayleigh scattering

Scattering rises with the fourth power of frequency, so short blue wavelengths scatter far more than red.

Q 02/05

Blue light has a dominant wavelength between roughly 450 and how many nanometres?

A) 420

B) 495

C) 550

D) 620

Answer · why

B) 495

Shorter blues drift towards violet, longer ones towards cyan.

Q 03/05

What was the first artificial pigment, produced in Egypt in the third millennium BC?

A) Prussian blue

B) Ultramarine

C) Egyptian blue

D) Cobalt blue

Answer · why

C) Egyptian blue

The Romans used it too; it turns up in the frescoes of Pompeii.

Q 04/05

Which two international organisations chose blue for their flags because of its association with harmony?

A) The UN and the EU

B) NATO and the Red Cross

C) The IOC and FIFA

D) UNESCO and the WHO

Answer · why

A) The UN and the EU

In languages, blue is usually the last basic colour term to be named, long after black, white and red.

Q 05/05

Ultramarine, the most expensive Renaissance pigment, was ground from which stone?

A) Turquoise

B) Lapis lazuli

C) Sapphire

D) Azurite

Answer · why

B) Lapis lazuli

It was reserved for the robes of the Virgin Mary and at times valued as highly as gold.