# Homework Help: Diffraction of water wave

1. Apr 19, 2013

### Deathnote777

1. The problem statement, all variables and given/known data
Suppose a water wave is moving from left to right in a water tank. The water tank is divided to two region (left and right) by an one-slit plastic plate. Which of the following(s) adjustment can increase the degree of diffraction of the wave ?

(1) Make the water of the whole tank deeper.
(2) Make the water in the right side deeper only.
(3) Make the water in the left side deeper only.

2. Relevant equations
Nil

3. The attempt at a solution
I know (1) must be correct as it can increase wavelength. But I am not sure whether (2) and (3) is correct or not, please explain. Thanks

2. Apr 19, 2013

### haruspex

Imagine you're a bit of the water just past the slit. Over time, what are you aware of wrt the movement of the water in the first half of the tank?

3. Apr 19, 2013

### Deathnote777

As far as I know, wavelength in deeper region will be longer. My teacher told me that the degree of diffraction will increase with the wavelength of waves. However, I don't know what will happen when making only 1 side deeper while another side remains unchanged.

4. Apr 19, 2013

### technician

you are right about the wavelength in deeper water being longer.

5. Apr 19, 2013

### haruspex

Yes, I understand that. Did you try to answer my question?

6. Apr 19, 2013

### Deathnote777

I don't really understand your question exactly. If I am a bit of the water and am passing through the slit, I will be diffracted, move away from the central line after passing through the slit

7. Apr 20, 2013

### haruspex

No, you're not passing through the slit, you're sitting on the surface just after the slit. (The wave moves, not the water.). What can you determine about the wave?

8. Apr 21, 2013

### Deathnote777

The wave will diffract

9. Apr 21, 2013

### haruspex

No, you're thinking like an external observer able to see the whole thing. I'm asking you to be a microscopic observer only able to see what's going on immediately after the slit. What do you experience? What can you tell about the wave wrt frequency, amplitude and wavelength?