Final answer:
Emma should investigate the relationship between a wave's frequency and its wavelength, which is option (c), to understand the key properties of waves that are essential for her design.
Step-by-step explanation:
The question Emma is trying to address relates to the properties and behaviors of waves. Given what we know about wave properties:
- The energy of a wave is directly related to its amplitude; larger amplitude means more energy.
- The amplitude and the frequency of a wave are independent of each other.
- As frequency increases, the wavelength decreases across the electromagnetic (EM) spectrum.
- The speed of a wave is the product of its wavelength and frequency, and it's unaffected by the amplitude of the wave.
Therefore, Emma could investigate the question, "What happens to a wave's frequency when its wavelength increases?" which is option (c). This question allows Emma to examine the inverse relationship between frequency and wavelength which does not involve changes in amplitude or energy.
This investigation takes into account that altering frequency has implications for the wavelength of a wave, recognizing that as one goes up, the other must come down. This principle is critical to understanding wave behavior and can directly impact Emma's design process.