Question 375
HardOriginal questionSunlight looks white, but it is really a mixture of all the colours of the rainbow, as anyone who has seen light pass through a knows. Light travels in waves, and the colours differ in the length of their waves: red light travels in long, lazy waves, while blue light travels in short, ones.
Light goes in a straight line unless something gets in its way. It may be , as by a mirror; bent, as by a prism; or , sent off in all directions. When sunlight enters the Earth's atmosphere, it meets the tiny of the gases that make up the air, and these scatter it. Blue light, with its shorter waves, is scattered far more than the other colours. So when you look at any part of the sky away from the Sun, what reaches your eyes is mostly this scattered blue light.
Near the , the sky looks paler, almost white. Light arriving from low in the sky has passed through much more air, and has been scattered again and again until the colours are mixed together once more.
The same idea explains a red sunset. When the Sun is low, its light has to cross a great thickness of air to reach you. By then, most of the blue has been scattered away, and the reds and yellows are left to come straight through.
Which of the following would the passage's explanation lead you to expect?
Show the answer and explanation
Correct answer: C
Explanation
The last paragraph says that when the Sun is low, its light crosses "a great thickness of air", most of the blue is scattered away, and the reds and yellows come through.
So at sunset, the light we see from the Sun's direction is reddish.
Worth noting
At midday the Sun is high and its light crosses the least air, so the passage's idea would lead us to expect a blue sky, not a red one.
- Concept
- Applying an explanation to a new case
- Typical timeTypical
- 60 s
- Your timeYours
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