When designing a device that utilizes the electromagnetic spectrum, several factors should be considered based on the specific application and required performance characteristics. Let's analyze each option provided:
A. A device using radio waves for communication should have longer wavelengths and higher frequencies.
- This statement is partially incorrect. While radio waves can be used for communication, longer wavelengths correspond to lower frequencies, not higher. For effective communication using radio waves, a balance between wavelength and frequency is needed, but typically, longer wavelengths (lower frequencies) can travel further and penetrate obstacles better.
B. A device using microwaves for food purposes should have shorter wavelengths than radio waves but lower frequencies.
- This statement is incorrect. Microwaves do indeed have shorter wavelengths than radio waves, but they actually have higher frequencies, not lower. Microwaves are used in cooking because they can excite water molecules effectively, absorbing energy at their frequencies.
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 very short wavelengths and high frequencies, which allows them to penetrate tissues. This quality makes them ideal for medical imaging to examine bones and other internal structures.
D. Cell phones used for communication should use waves that have shorter wavelengths and higher frequencies.
- This statement is generally correct as well. Cell phones utilize higher frequency electromagnetic waves, which correspond to shorter wavelengths. This enables more data to be transmitted over the same distance and allows for more efficient communication.
Based on the analysis, the most accurate statements related to practicality for their respective uses are:
- C is correct for x-rays used for medicinal purposes.
- D is also correct for cell phones used for communication.
However, if the goal is to identify the most practical consideration specifically for each type of device, option C could be highlighted as particularly crucial for the medical context as it directly pertains to safety and efficacy in diagnostics.