AQA GCSE Physics

Revision Notes

6.2.8 Dangers of High-Energy EM Waves

Hazardous Effects of High-Energy EM Waves

  • As the frequency of electromagnetic (EM) waves increases, so does the energy
  • Beyond the visible part of the spectrum, the energy becomes large enough to ionise atoms
  • As a result of this, the danger associated with EM waves increases along with the frequency
    • The shorter the wavelength, the more ionising the radiation
    • Although the intensity of a wave also plays a very important role

EM Waves Energy, downloadable IGCSE & GCSE Physics revision notes

Ultraviolet, X-rays and gamma rays can all ionise atoms

  • Because of ionisation, ultraviolet waves, X-rays and gamma rays can have hazardous effects on human body tissue
    • The effects depend on the type of radiation and the size of the dose
  • They can damage cells and cause mutations, making them cancerous

Radiation Dose

  • Radiation dose is defined as:

A measure of the risk of harm resulting from an exposure of the body to ionising radiation

  • Radiation dose is measured in sieverts (Sv)
    • 1 Sv is a very large amount of radiation, so it is more commonly measured in millisieverts (mSv) where 1 Sv = 1000 mSv
    • Typically, background radiation is about 1.5 to 3.5 mSv per year
    • Whereas, 8 Sv is enough to cause death, even with treatment

Dangers of UV, X-rays & Gamma Rays

  • In general, electromagnetic waves become more dangerous the shorter their wavelength
    • For example, radio waves have no known harmful effects whilst gamma rays can cause cancer and are regarded as extremely dangerous
  • The main risks associated with electromagnetic waves are summarised in the table below:

Dangers of EM Waves TableEM Waves Dangers Table, downloadable IGCSE & GCSE Physics revision notes

Microwaves

  • Certain frequencies of microwaves are absorbed by water molecules
  • Since humans contain a lot of water, there is a risk of internal heating from microwaves
  • This might worry some people, but microwaves used in everyday circumstances are proven to be safe
    • Microwaves used for communications (including mobile phones) emit very small amounts of energy which are not known to cause any harm
    • Microwave ovens, on the other hand, emit very large amounts of energy, however, that energy is prevented from escaping the oven by the metal walls and metal grid in the glass door

Ultraviolet

  • Ultraviolet is similar to visible light, except it is invisible to the human eye and carries a much higher energy
  • If eyes are exposed to high levels of UV it can cause severe eye damage
    • Good quality sunglasses will absorb ultraviolet, preventing it from entering the eyes
  • Ultraviolet is ionising meaning it can kill cells or cause them to malfunction, resulting in premature ageing, and diseases such as skin cancer
    • Sunscreen absorbs ultraviolet light, preventing it from damaging the skin

X-rays & Gamma Rays

  • X-rays and gamma rays are the most ionising types of EM waves
    • They are able to penetrate the body and cause internal damage
    • They can cause the mutation of genes and cause cancer
  • Fortunately, the level of X-rays used in medicine is kept to minimum levels at which the risk is very low
    • Doctors, however, will leave the room when taking X-rays in order to avoid unnecessary exposure to them
  • People working with gamma rays have to take several precautions to minimise their exposure and are routinely tested to check their radiation dose levels
  • For example, radiation badges are worn by medical professionals such as radiographers to measure the amount of radiation exposure in their body

radiation-badge, IGCSE & GCSE Physics revision notes

Radiation badges are used by people working closely with radiation to monitor exposure

Risks & Consequences of Radiation Exposure

  • A part of the scientific process is the ability to draw conclusions from given data
  • When interpreting data about the risks and consequences of exposure to radiation it is important to consider the following questions:
    • What are the known risks and consequences of the type of radiation being discussed?
    • Does the data correlate to the hypothesis?
    • Are there other factors that could explain the results?

Worked Example

Some scientists suggest there is a possible link between using a mobile phone and male fertility. The results of their study are given in the table below.

WE Mobile Phone Data, downloadable IGCSE & GCSE Physics revision notes

Evaluate this data and make a conclusion as to whether or not there is a link between mobile phone use and male fertility. Make suggestions that could improve the reliability of the results.

Step 1: Identify the type of EM wave and the known risks

    • Mobile phones use microwaves
    • The known risks are possible internal heating at sufficiently high energies

Step 2: Identify if there is a correlation in the data or not

    • The results show a negative correlation: the more hours a mobile phone is used each day, the lower the sperm count

Step 3: Identify any other factors that could explain the data

    • Many factors can cause a reduction in sperm count for example:
      • High-stress environment
      • Exposure to heat
      • Sedentary lifestyle
      • Health problems that affect fertility e.g. hormonal imbalance
      • Medication
      • Obesity
      • Smoking / alcohol / drug intake
      • Diet
      • Age

Step 4: Write a conclusion

    • The data shows a negative correlation, but there is not enough known about the testing methods and other factors that could affect the results
    • Therefore, the results do not necessarily mean using a mobile phone causes a reduced sperm count

Step 5: Make suggestions for improvements

    • Use a larger sample size
    • Take into account the other affecting factors and investigate control samples i.e. healthy men, men under 30, men who smoke
    • Make sure to compare the health of mobile phone users with non-mobile phone users to make it a fair test

Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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