Site for children


J. Perelman
"Entertaining physics". Book 1.
Chapter 8. Reflection and refraction of light

USING SUNLIGHT

Do still experience too easy in the winter. Put on the snow, flooded with sunlight, two equal size scraps of fabric, bright and black. After an hour or two you make sure the black cloth was immersed in the snow, while the light remained on the same level. Seeking the causes of such differences is easy: under the black shred the snow melts stronger, because dark fabric absorbs most of the incident sunlight; light, on the contrary, most of them scatters and therefore weaker heated than black.

Instructive experience for the first time this has been done was a famous fighter for the independence of the United States Benjamin Franklin, has immortalised himself as a physicist, the invention of the lightning rod. “I took the tailor several square pieces of cloth of different colors, " he wrote. Among them were: black, dark blue, light blue, green, purple, red, white and various other colors and shades. One bright Sunny morning, I put all these pieces on the snow. After a few hours the black piece, heated stronger than others, sank so deep that the Sun's rays more was not achieved; dark blue sank almost as much as black; light blue is much less; other colors fell less than they are lighter. White remained on the surface, i.e., not dropped”.

“What good would the theory, if it was impossible to extract any benefit? - he cries about it and says, " why can't we from this experience to bring that black dress in a warm Sunny climate is less suitable than white because it is the stronger sun heats our body, and if we are still going to do the movements, which themselves us warm, there is excessive heat? Shouldn't men's and women's summer hats to be white in order to eliminate the heat, which causes some sunstroke?.. Next, wycinanie walls may not do to absorb during the day as much solar heat that night to stay somewhat warm and protect the fruit from frost? Can't do a careful observer to stumble on other particular greater or lesser importance?”

What can be these conclusions and useful application that shows the example of the German South polar expedition, 1903, aboard the “Gauss”. Ship frozen in the ice, and all the usual ways of liberation has not led to any results. Explosives and saws, put in the case, removed only a few hundred cubic meters of ice and did not release the ship. Then turned to the sun's rays from dark ash and coal staged on ice band at 2 kilometres long and ten meters wide; it led from the ship to the nearest big crack in the ice. Were clear long days of the Arctic summer, and the sun's rays did what the could not make dynamite and saw. Ice podav, broke down along the scattered bands, and the ship became ice-free.

Entertaining physics J. Perelman

 




System Orphus

SUPPORT THE SITE!

Did you like our site and you would like to support it? It's very simple: tell your friends about us!
Read MORE

  © 2014 All children