# The perfect wave — and why this is not a fake image

This picture might look fake, but it’s not.

But what about it does scream “fake!”? To me, there are several things:

• the almost perfect sinusoidal shape of the waves
• the way how wavelengths and amplitudes decrease with distance
• the almost complete lack of other waves except for the one dominant field
• the way we can look into the water and see the jungle beneath the waves

Of course, all of these can be explained:

• the almost perfect sinusoidal shape of the waves: We are used to seeing waves that have longer troughs and pointier crests. The waves we see here are the wake of a small boat which caused a large disturbance that then propagates over the lake, keeping its shape fairly well.
• the way how wavelengths and amplitudes decrease with distance: Usually when we see wave heights increasing towards the shore, we would at the same time see wavelengths decreasing since the increasing wave height would be due to the waves running up a slope and being slowed down. In deep water (i.e. water deeper than a wavelength, which is the case here), longer wavelengths propagate faster than shorter ones, therefore longer waves outrun shorter ones. And the leading wave is the actual wake, the largest disturbance, whereas later waves are just oscillations before the surface comes back to rest.
• the almost complete lack of other waves except for the one dominant field: Usually we would expect to see a bunch of different wavelengths occurring at the same time if we were looking at a wind generated wave field, but in this case we are looking at a dominant wave field created by a boat. There was almost no wind that day; wind waves are just the small ripples perpendicular to the dominant wave field.
• the way we can look into the water and see the jungle beneath the waves: this is due to a phenomenon called total internal reflection. Spooky, isn’t it?

Here is how the waves developed over time from when the boat passed by until they reached the jetty on which I was sitting:

I really like another way of looking at that wave field, and that is how my camera roll shows them. Which wave picture of all of these is your favourite?

This is my personal favourite: