Answer:
A. The wavelength doubles but the wave speed is unchanged
Explanation:
The relationship between the period and wavelength is direct. Doubling the period of the oscillator will correspondingly double the wavelength but the wave speed is unaffected
Let's see: frequency of cellular phone waves (GSM phones) is (800-1900 MHz). If we look at the table of the electromagnetic spectrum, we can see that this range is contained within the frequencies of the microwaves, which include waves in the range 300 MHz-300 GHz.
So, summarizing, the correct answer is "microwaves".
If you mean like electromagnetic waves then, Mico waves, UV rays, and infrared waves
