Wave properties diagram showing key terms such as crest, trough, amplitude, wavelength, and equilibrium line with definitions.

Let's solve this step by step.

We are given a wave diagram and a list of words to use to label parts of the wave and complete definitions. The words are:

Words to use:
- Hertz
- period
- metres
- dip
- seconds
- peak
- wavelength
- trough
- crest
- amplitude
- oscillation
- equilibrium line

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Step 1: Label the Diagram

Looking at the wave diagram:

1. Top of the wave: This is called the crest (or peak – both are synonyms in wave terminology).
2. Bottom of the wave: This is the trough.
3. The horizontal dashed line: This is the equilibrium line (also called the rest position).
4. Distance between two consecutive crests (or troughs): This is the wavelength.
5. Vertical distance from the equilibrium line to the crest (or trough): This is the amplitude.
6. The time for one full cycle (not shown directly, but implied): This is the period, measured in seconds.
7. Number of waves per second: This is frequency, measured in Hertz.

Now let’s fill in the diagram:

- Top arrow pointing to the highest point of the wave → crest or peak
- Arrow pointing to the lowest point → trough
- Horizontal dashed line → equilibrium line
- Distance from one crest to the next → wavelength
- Vertical distance from equilibrium line to crest → amplitude

So, labeling the boxes:

1. Top horizontal arrow (from crest to crest) → wavelength
2. Vertical arrow from equilibrium line to crest → amplitude
3. Dashed line → equilibrium line
4. Lowest point of wave → trough
5. Highest point of wave → crest (or peak)

But note: there are four blank boxes on the diagram. Let's match them based on typical labeling:

- Leftmost box (pointing to dashed line) → equilibrium line
- Top horizontal arrow (between two crests) → wavelength
- Vertical arrow (from equilibrium to crest) → amplitude
- Bottom right box (pointing to lowest point) → trough

So:

```
[ wavelength ] ← top horizontal arrow
[ amplitude ] ← vertical arrow
[ equilibrium line ] ← left box (dashed line)
[ trough ] ← bottom right box
```

Also, the crest or peak is labeled at the top of the wave — it might be implied, but if there’s a box at the top, it would be crest or peak.

But since only four boxes are shown, we assume:

- Top horizontal: wavelength
- Vertical: amplitude
- Dashed line: equilibrium line
- Trough: trough

(And "crest" or "peak" may be used in the definitions.)

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Step 2: Complete the Definitions

Now, fill in the blanks below:

1. ______ - the top of a wave
→ crest or peak
✔ Use crest or peak — both acceptable. Let's use crest.

2. ______ - the bottom of a wave
→ trough

3. ______ - the level if the wave flattened out
→ equilibrium line

4. ______ - a repeated action back and forth or up and down
→ oscillation

5. ______ - the number of waves that pass every second (measured in ______)
→ frequency (measured in Hertz)

6. ______ - the time it takes for one complete wave to pass (measured in ______)
→ period (measured in seconds)

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✔ Final Answer:

#### Diagram Labels:
- Top horizontal arrow (crest to crest): wavelength
- Vertical arrow (equilibrium to crest): amplitude
- Dashed line: equilibrium line
- Bottom right (lowest point): trough

*(Note: "crest" or "peak" may also be labeled at the top of the wave, but not boxed unless indicated.)*

#### Definitions:

1. crest – the top of a wave
2. trough – the bottom of a wave
3. equilibrium line – the level if the wave flattened out
4. oscillation – a repeated action back and forth or up and down
5. frequency – the number of waves that pass every second (measured in Hertz)
6. period – the time it takes for one complete wave to pass (measured in seconds)

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✔ Words Used:

- wavelength – used once (diagram)
- amplitude – used once (diagram)
- equilibrium line – used once (diagram & definition)
- trough – used twice (diagram & definition)
- crest – used once (definition)
- oscillation – used once (definition)
- frequency – used once (definition)
- Hertz – used once (in frequency definition)
- period – used once (definition)
- seconds – used once (in period definition)

Unused: peak, dip, metres

> Note: "peak" is synonymous with "crest", so it could be used instead of "crest" in the first definition. But "dip" is not standard; "trough" is correct. "Metres" is a unit of length (e.g., for wavelength or amplitude), but not needed here as units aren't asked for in the diagram labels.

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✔ Final Answer Summary:

Diagram Labels:
- Wavelength (top horizontal)
- Amplitude (vertical)
- Equilibrium line (dashed line)
- Trough (bottom)

Definitions:
1. crest – the top of a wave
2. trough – the bottom of a wave
3. equilibrium line – the level if the wave flattened out
4. oscillation – a repeated action back and forth or up and down
5. frequency – the number of waves that pass every second (measured in Hertz)
6. period – the time it takes for one complete wave to pass (measured in seconds)