Question

1a)radar communications and cell phones (mobile phones) use which type of electromagnetic radiation? explore the internet (or chatgpt) to find the answer. (but make sure you understand the material presented by the source you used; also, make sure to mention/cite which source you used). 1b) which radiation will have higher frequency (or energy) among a 420 nm wavelength radiation and a 750 nm wavelength and why? (hint: think about the relationship between energy and wavelength; is it directly proportional or inversely proportional)

Explanation:

1a)

Radar communications and cell phones use radio waves (a type of electromagnetic radiation). Source: National Institute of Standards and Technology (NIST) website (https://www.nist.gov/), which explains that radar and mobile phones operate in the radio frequency range of the electromagnetic spectrum, utilizing radio waves for signal transmission and reception. Radio waves have relatively long wavelengths and low frequencies compared to other electromagnetic radiation types like visible light or X - rays, making them suitable for long - distance communication and penetrating obstacles to some extent.

Step1: Recall the relationship between energy, frequency, and wavelength

The energy of electromagnetic radiation is given by the formula $E = hf=\frac{hc}{\lambda}$, where $E$ is energy, $h$ is Planck's constant, $f$ is frequency, $c$ is the speed of light, and $\lambda$ is the wavelength. From this formula, we can see that energy ($E$) and frequency ($f$) are directly proportional ($E\propto f$), and both energy and frequency are inversely proportional to wavelength ($E\propto\frac{1}{\lambda}$, $f\propto\frac{1}{\lambda}$).

Step2: Compare the wavelengths

We are given two wavelengths: $\lambda_1 = 420\space nm$ and $\lambda_2=750\space nm$. Since $420\space nm<750\space nm$, and frequency is inversely proportional to wavelength ($f = \frac{c}{\lambda}$), a smaller wavelength will correspond to a higher frequency.

Answer:

Radar communications and cell phones use radio waves (a type of electromagnetic radiation). (Source: National Institute of Standards and Technology (NIST) website, https://www.nist.gov/)

1b)