### Part a: Define a Ray
A ray is a line which starts from a point and moves infinitely in one direction without having a definite width or thickness. In physics, particularly in optics and wave theory, a ray often represents the path along which light or other waves propagate.
### Part b: Calculating the Period
To calculate the period ([tex]\(T\)[/tex]) of a wave, we use the relationship between frequency ([tex]\(f\)[/tex]) and period. The period is the reciprocal of the frequency.
Given:
- Frequency ([tex]\(f\)[/tex]): 300,000 Hz (or 300 kHz)
- Speed of wave ([tex]\(v\)[/tex]): 3.000 m/s
Here, the speed of the wave is not directly used in calculating the period when frequency is given, but it is good to understand that speed ([tex]\(v\)[/tex]), frequency ([tex]\(f\)[/tex]), and wavelength ([tex]\(λ\)[/tex]) are related by the equation [tex]\(v = f \lambda\)[/tex]. However, for the period calculation, the focus is on frequency and period.
The formula to find the period ([tex]\(T\)[/tex]) is:
[tex]\[ T = \frac{1}{f} \][/tex]
Substitute the given frequency into the formula:
[tex]\[ T = \frac{1}{300,000 \text{ Hz}} \][/tex]
Now, perform this division to find the period:
[tex]\[ T = 3.3333333333333333 \times 10^{-6} \text{ seconds} \][/tex]
Thus, the period ([tex]\(T\)[/tex]) of the wave is [tex]\(3.3333333333333333 \times 10^{-6}\)[/tex] seconds.
