As waves travel into the denser medium, they slow down and wavelength decreases.
Part of the wave travels faster for longer causing the wave to turn.
The wave is slower but the wavelength is shorter meaning frequency remains the same.
Think of it this way:
The source (whatever) send out a wave every second.
So they will keep coming at one a second.
That is the frequency, 1 Hz.
Just doing something that affects the wavelength of the waves after they have been sent won’t affect the frequency, basically they will keep arriving at one per second because they are one second apart.
Changing the wavelength differentially along the length of a wavefront is a trick that can make it turn a bit of a corner – refraction, but that has no effect on the frequency.
The colour of light is an effect of its wavelength upon the eye. Therefore differential refraction causes the light to spread into a rainbow as different wavelengths refract by different angles.
In this diagram, the right hand side of the incoming wave slows down before the left hand side does. This causes the wave to change direction.
Credit to BBC bitesize for the diagram and some of the explanation of refraction –
Now listen up ‘cos this is important…
The refractive index of air changes as humidity increases.
Liquid water (eg raindrops) refractive index is equal to a number which is 1.33 and for the humid air the number is generally in the 1-1.33 range. Yes that’s right, it can be 1.33, exactly the same as the water. When the numbers are the same you don’t get any refraction, so no rainbow. So if the air is very humid, no rainbows.
When no bush of the field was yet in the land and no small plant of the field had yet sprung up—for the Lord God had not caused it to rain on the land, and there was no man to work the ground, and a mist was going up from the land and was watering the whole face of the ground.
So pre-flood the air was very humid so there were no rainbows, then the fountains of the deep opened and the huge amount of dust that would have been sent into the atmosphere by these enormous space-reaching fountains like those we see on Jupiter’s moon Europa.
These fountains were caused in the case of Earth by the collapse of the outer crust/upper mantle onto the lower mantle, forcing down onto the underground ocean 350-450 miles down that could only then escape by fountaining out at incredible pressure upwards like a volcano – the remnant of which underground ocean is now trapped into a layer of rock called ringwoodite, and is of course some of the water now also exists above ground as the familiar oceans such as the Atlantic and Pacific that cover 3/4 off the world, a covering that was not formerly present.
This eruption of water would have provided a huge injection of dust into the atmosphere, giving nucleation sites to form droplets, clouds and eventually rain. Water vapour needs little specks of dust to form droplets. This means that water collects together out of solution, making the air less humid, allowing than for rainbows to form.
By faith Noah, being warned by God concerning events as yet unseen, in reverent fear constructed an ark for the saving of his household.
The thing he had not yet seen was rain, but when it came it was a deluge for not only were there the fountains of the deep crashing back to earth all the way from orbit, normal rain started as well.
These events of course completely transformed the earth geologically giving us the mountains oceans and continents we have today. The upheavals that started with the cracking and collapse of the other crust split it into the moving tectonic plates we now know.
All this is the result of the hot earth thinking as it cooled.
So, what the bible says about the flood is generally supported by the sciences of geology, astronomy (eg Io), meteorology (details like nucleation) and physics (refractive indices). One of course would expect nothing less if the Bible is true.
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