Q 01/05

Roughly how fast does light travel through empty space?

A) About 300 km per second

B) About 3,000 km per second

C) About 300,000 km per second

D) About 30 million km per second

Answer · why

C) About 300,000 km per second

Light travels at about 300,000 km per second through empty space, exactly 299,792,458 metres per second; since 1983 the metre has been defined from th...

Q 02/05

Whose three laws of motion were first published in the Principia in 1687?

A) Johannes Kepler

B) Galileo Galilei

C) René Descartes

D) Isaac Newton

Answer · why

D) Isaac Newton

Isaac Newton set out the three laws in Philosophiae Naturalis Principia Mathematica, written in Latin and published in 1687, alongside universal gravi...

Q 03/05

Which SI unit, symbolised by the Greek letter omega, measures electrical resistance?

A) Volt

B) Farad

C) Ampere

D) Ohm

Answer · why

D) Ohm

The ohm honours the German physicist Georg Ohm, whose 1827 law links voltage, current and resistance; one ohm passes one ampere under one volt.

Q 04/05

What phenomenon makes the daytime sky look blue?

A) Rayleigh scattering

B) Refraction by water vapour

C) Fluorescence of ozone

D) Total internal reflection

Answer · why

A) Rayleigh scattering

Rayleigh scattering by air molecules affects short blue wavelengths far more than long red ones, so scattered blue light fills the sky; the low Sun tu...

Q 05/05

At 20 °C, how fast does sound travel through air?

A) About 143 metres per second

B) About 343 metres per second

C) About 743 metres per second

D) About 1,043 metres per second

Answer · why

B) About 343 metres per second

Sound moves at about 343 metres per second in air at 20 °C, roughly a kilometre every three seconds, which is why you count between lightning and thun...