Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question 11 - 2010

To calculate the Specific Absorption Rate (SAR), we use the formula:

ext{SAR} = rac{ ext{Power}}{ ext{mass}}

First, we calculate power:

ext{Power} = rac{0.36 ext{ J}}{180 ext{ s}} = 0.002 ext{ W}

Then substituting values:

ext{SAR} = rac{0.36 ext{ J}}{(10 imes 10^{-3} ext{ kg})(180 ext{ s})} = 0.20 ext{ W kg}^{-1}

The radio frequency energy absorbed by the body is primarily converted into heat. This energy increases the temperature of the tissues that absorb it.

Radio frequency waves have a low frequency and a long wavelength, which makes them less penetrating compared to higher frequency waves. The longer wavelengths tend to reflect off surfaces rather than penetrate deeply into materials, including human tissues.

The audible frequency limits for sound waves are generally from about 20 Hz to approximately 20,000 Hz (20 kHz).

1. Keep the phone at a distance, such as using a loudspeaker function or headset.

2. Avoid prolonged direct exposure to the phone by taking breaks during calls.

To find the length of the antenna, we can use the formula:

ext{length} = rac{c}{f}

Where:

• $c$ is the speed of light, approximately $3.0 imes 10^8 ext{ m s}^{-1}$
• $f$ is the frequency, $1200 imes 10^6 ext{ Hz}$.

First, we calculate the wavelength:

ext{wavelength} = rac{3.0 imes 10^8 ext{ m s}^{-1}}{1200 imes 10^6 ext{ Hz}} \\ = 0.25 ext{ m}

Now, the length of the antenna, which is one quarter of the wavelength, is:

ext{length} = rac{0.25 ext{ m}}{4} = 0.0625 ext{ m} = 6.25 ext{ cm}

An example of an electromagnetic wave that may induce cancer is X-rays. X-rays have high energy and are ionizing radiation that can cause ionization of body cells, potentially leading to mutations and cancer.