1. Given the distance scale in micrometers (1.0×10^-6m), shown in the figure, what is the wavelength in meters per wave?
2. Given that 6.0×10^8 crests of wave pass a point in 1.0 microsecond, what is the value of the frequency of this wave/sec (or Hz)?
3. Calculate the product of the answers to Q1 and Q2 above.
4. What is the significance of the value just calculated?
For Q1 and Q2, with help from the teacher, I got the answers: 0.5 m/s and 6.0×10^14 Hz. I just need to know how to do # 3 and how to answer # 4.
The wave below is used to answer the questions.

1. Wavelength is the distance between two successful crests or troughs in a transverse waves (wave motion is perpendicular to the direction of wave motion), and the distance between two successful rarefactions or compressions in a longitudinal wave ( wave motion is parallel to the direction of the wave).
In this case; the distance between two successful troughs is 0.5 × 10 ^-6 m.

2. Frequency is the number of complete oscillations in one seconds. In this case a complete oscillation occurs after every two successful crests or troughs. Therefore; the frequency will be;.
1.0 × 10^-6 sec = 6.0 × 10^ 8 crests
Thus; 1 sec = (6.0 × 10^8 crests)/ (1.0 × 10^-6 sec)
Hence; the frequency is 6 × 10^14 Hz

3. Multiplying the answer in question 1 and 2; that is multiplying the value of wavelength and frequency we get;
0.5 × 10^-6 × 6 ×10^14 = 3 ×10 ^8 m/s

4. When you multiply the frequency of a wave and its frequency you get the speed of that particular wave;
That is; speed = frequency × wavelength
Thus; the speed of the above wave is 3.0 ×10^8 m/s; which means the wave is an electromagnetic wave since it has a speed of light (3.0 ×10^8 m/s)