## Water waves - is this reflection, or refraction, or both?

Now my understanding is that water slows down when it goes over a shallow area because the ground under the shallow water is interfering with the wave. When this happens the wave becomes more transverse which I guess is due to reflection as the wave is hitting the ground under it, perhaps the bottom part of the wave is being reflected and the rest of it is not.

When the slide is at an angle why is it refraction and not reflection since the wave is actually hitting it the glass slide?

It becomes abit more confusing when you take into account that the top of the wave is travelling through air (the more transverse the wave is the more this happens), and the rest of it is travelling through water, which might result in refraction too, but the image suggests the slide is the cause of the refraction.

 Quote by Steve143 When the slide is at an angle why is it refraction and not reflection since the wave is actually hitting it the glass slide?
From the picture, I'm kind of getting that the glass slide is placed horizontally (parallel to the ground) and so the depth in that area is less than in the tank as a whole. Having the slide at an angle just bends the phase lines (and hence the nominal ray path). Is that what you see?

 It becomes abit more confusing when you take into account that the top of the wave is travelling through air (the more transverse the wave is the more this happens)
How do you get that?

The way i'm interpreting it like this:

 If a small glass is plate is placed in the centre of the ripple tank, the depth of the water is reduced. As waves enter this region we can see that their wavelength becomes shorter
when the slide is flat on the bottom of the tank the wavelength is reduced. (as far as I know this is because the wave touches the bottom and is probably reflected off it)

 if the bountry between the shallow water and the deep water is at an angle to th direction in which the waves are moving, the direction of the waves changes. We say the waves have been refracted
When the slide is at an angle the wave is refracted.

 How do you get that?
I think of sea waves, the parts of the wave that are higher than the rest of the water are moving through air

 Waves through the water are oscillations in the displacement of the water molecules, up and down - it is not possible in any at all straight-forward way for such waves to propagate through into a solid medium like glass, as would have to occur for the waves to be refracted. Of course a solid like glass can support oscillations travelling through it, but at frequencies so very much higher than those you would create in a ripple tank (approx a million times) that on meeting the glass, the wave would essentially be entirely reflected.

## Water waves - is this reflection, or refraction, or both?

 Quote by Steve143 The way i'm interpreting it like this: when the slide is flat on the bottom of the tank the wavelength is reduced.
I think you may be misreading the description:

"If a small glass is plate is placed in the centre of the ripple tank, the depth of the water is reduced."

The glass plate is parallel to the bottom but not flat on the bottom (or else why would it matter?). This makes the water above the glass plate effectively shallower.

 (as far as I know this is because the wave touches the bottom and is probably reflected off it)
It's because the phase speed of shallow water waves decreases as the water depth gets smaller.

 When the slide is at an angle the wave is refracted.
Figure 11.16 is a top down view. From the description:

"If the boundary between the shallow water and the deep water is at an angle to the direction in which the waves are moving, the direction of the waves changes."

The bending of the wave direction is just like the bending of light rays as they pass through an pair of interfaces or a lens or whatever.

 I think of sea waves, the parts of the wave that are higher than the rest of the water are moving through air
As it happens, the water particles are hardly moving at all. But this has nothing at all to do with the wave refraction effect being described.

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