Frequently Asked Questions: Light and Optics

Q. What is the speed of light in a vacuum?
A. 300 000 kilometres per second

Q. Why do cricketers wear white clothing?
A. It is cooler than other colours. White clothing reflects almost all light, so that little or no light is absorbed by the clothing and converted to heat.

Q. What foods are best suited for microwave cooking?
A. Microwaves are very effective in cooking foods containing a lot of water.

Q. Why are soap bubbles white?
A. There's less light inside a bubble than outside. The surface acts like a mirror reflecting all light, in a way similar to a house window in daytime.

Q. Why is cloth darker when wet?
A. Less light is reflected from wet cloth so it appears darker.

Q. How do some animals make their own light?
A. Some animals have a chemical called luciferin that reacts with oxygen to emit light. This process is called bioluminescence.

Q. Brown bread and white bread toast equally in a toaster, yet brown toast appears much darker than white toast. Why?
A. Less light is reflected from brown bread than from white bread, so it appears darker.

Q. Who was the only father and son team to win a Nobel Prize for physics by identifying the structure of crystals using X-ray diffraction?
A. Sir William Henry Bragg (father) and Sir William Lawrence Bragg (son)

Q. What is a photon?
A. A photon is a particle of particle that is thought to have no mass but a speed of 300 000 km/s in a vacuum.

Q. What is a mirage?
A. A mirage is caused by refraction of sunlight as it passes from the higher cooler air through the moving steamy hot air near the surface of the desert or a road.