There are only seven colours in a rainbow because only seven colours are included on the visible spectrum. Why Are There Only Seven Colours in a Rainbow?
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If you were in an airplane and saw a rainbow below you, it would appear as a full circle. Because you are on Earth, part of the sun is blocked, which why rainbows appear as a half or a quarter circle. This causes water to be attracted to many surfaces and also explains many other properties of water.Ī rainbow is curved because it reflects the round shape of the sun. Water is polar-it has an uneven spread of electrical charge-which makes one end of the molecule positive and the other end negative. they stick to many solid surfaces) due to the electrostatic (opposite charges) forces between molecules. Dip one index finger in each liquid, lift them out, and then observe for a few minutes." (Young children should ask an adult to help.) Let both liquids come to room temperature for a day, or overnight. Fill two small cups: one with water, and the other with cooking oil. You can test this by comparing water with another liquid such as cooking oil, which doesn't evaporate so freely. "The feeling of wetness is actually coldness. Below is an experiment from the Institute of Physics to test the feeling of "wetness" between two different liquids: What we feel as wetness is actually coldness as the water evaporates. "Wet" is ultimately just a word that applies to water. "Wet" is just a term people use to describe the feeling of water. If the pilot were to engage the thrust reverser while parked in the gate, the amount of force coming from the thrusters would damage the airport as well as the people and vehicles on the ground. When an airplane backs out of a gate at an airport, it relies on the use of tow cars to push it onto the runway. Airplane pilots usually only use this function for stopping once they land. They a "thrust reverser" which changes the direction of the spinning blades in the thruster so that air is thrust forward instead of back. Can an Airplane Go in Reverse?Īirplanes can in fact go in reverse. An airplane, too, can appear to stand still if there is a strong headwind coming towards it that keeps it in place. A helicopter, for example, appears to stand still in the air as its propeller pulls the aircraft up at the same rate gravity pulls it down. Everything is always falling, but an aircraft can appear to stand still in the air by stabilizing its altitude. This is a rule outlined by the laws of physics. When mixed together, our eyes are only able to see the dominant colour: blue.Īn airplane cannot stand still in the air. The sky is dominated by wavelengths between 400 nanometers (violet) and 450 nanometers (blue). It is true that violet is being scattered in the sky much like blue, but our eyes are not refined enough to see every colour of the spectrum. This is a frequently asked question, though, because according to the general answer to the question of the sky's colour (that because blue has a short wavelength it is caught and reflected in the sky), violet should be seen too, since its wavelength is even shorter than blue's. Simply by looking up, we can see that the sky is indeed blue and not purple. The main component of this kind of pollution is nitrogen dioxide. Smoke from forest fires or agricultural burns can cause the sky to appear this colour.Įmissions from cars and trucks can cause a layer of this colour to form over the horizon. There are also natural causes, such as volcanic activity or ocean plankton. This condition often occurs in the summer when the air is still. This colour indicates considerable air pollution from coal-burning power plants or chemical power plants. Lastly, it may be caused by the chemical emissions of plants and trees, such as those found in The Smokey Mountains of North Carolina and Tennessee. It can also suggest the presence of sulfur from coal-burning operations. This colour means there is lots of water vapor in the sky. This often occurs when a cold front brings clean air from the north, or when clean air from the ocean moves onto land. The colours of the daytime sky and the causes of its varying colour.