When designing a device using the electromagnetic spectrum, it's essential to select the appropriate wavelengths and frequencies based on the intended application of the device. Let's analyze the options:
A. A device using radio waves for communication should have longer wavelengths and higher frequencies.
- This statement is incorrect because, while radio waves typically have longer wavelengths, they correspond to lower frequencies. Thus, it should state that radio waves have longer wavelengths and lower frequencies.
B. A device using microwaves for food purposes should have shorter wavelengths than radio waves but lower frequencies.
- This statement is misleading as microwaves do have shorter wavelengths than radio waves, but they also have higher frequencies, not lower.
C. A device using x-rays for medicinal purposes requires waves that have shorter wavelengths and higher frequencies.
- This statement is correct. X-rays have short wavelengths and high frequencies, making them suitable for medical imaging.
D. Cell phones used for communication should use waves that have shorter wavelengths and higher frequencies.
- This statement is also correct. Cell phones typically operate at frequencies that correspond to shorter wavelengths, allowing for efficient communication.
Based on the considerations for practicality in device design, the correct evaluations would be:
- C (for X-rays) and D (for cell phones) are accurate statements regarding the appropriate use of the electromagnetic spectrum for their respective applications.
Overall, if you seek to pick the most directly appropriate for a specific application, C is a clear and focused choice regarding medical use.