Top 10 light factsLight quiz
Who should you expect to show stronger red-eye effect?
Blue-eyed people. The iris plays no role in the effect, but the blue-eyed people have relatively low melanin in the fundus as well. Therefore, they show a much stronger red-eye effect, as the light passing fundus is not absorbed by melanin. The role of melanin in red-eye effect is nicely demonstrated in case of heterochromia (one eye blue, one brown): typically, only the blue eye displays the effect.
Is the speed of light photons always constant?
A speed of light is always constant. The speed at which light propagates through transparent materials, such as glass or air, is less than c. However, this "slowing of the light" is only due to the fact of photos being absorbed and re-emitted after a slight delay between atoms. When a photon is emitted, it's speed is always c. In exotic materials like Bose–Einstein condensates near absolute zero, the effective speed of light may be only a few metres per second.
What are the most luminous objects in the universe?
Quasars. A quasar is an extremely energetic source of radiation powered by accretion disc around galaxy's central supermassive black hole. Quasars were much more common in the early universe, as all known quasars are extremely distant.
What photographic technique was used to create this photo?
Light painting. The photo was taken with long exposure. For the first 15 seconds, the author hold still with lights on, to achieve the light in the background. Later, he switched off the light and wrote his name with light in his hand. He used his nose as a reference point so he could close the "O" letter - which explains the flare at this position.
In what process sky colors (including blue sky and red sun) are created?
Rayleigh scattering, named after the British physicist Lord Rayleigh (John William Strutt), is an elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation.
Which of the following is the worst for eyesight during a sunny day?
Wearing sunglasses without UV filter causes the pupils to dilate and eyes to absorb more UV rays than they normally would without the sunglasses. Hence, it's much better not to wear sunglasses at all, than to wear ones without UV filter.
How many typical stars can supernova be luminous as?
One hundred billion stars. Supernovae are extremely luminous and often briefly outshine an entire galaxy. No supernova has been observed in the Milky Way since 1604, but they are often observed in distant galaxies.
What kind of building is that?
Solar power plant. In The PS10 Solar Power Plant, 624 movable mirrors concentrate the sun's rays to the top of a 115 meter (377 ft) high, the tower where a steam turbine is located. The plant is located near Seville, Spain.