4.6.2.3 Properties of Electromagnetic Waves 2

Question 1

How are EM waves generated through atomic changes?

Answer 1

• changes in atoms and the nuclei of atoms can result in EM waves being generated or absorbed over a wide frequency range
  1. Electrons are arranged at different distances from the nucleus (in different energy levels)
  2. When electrons absorb EM radiation they move further from the nucleus to a higher energy level
  3. As the electron is unstable at a higher energy level it drops back down to its original energy level
  4. As the electron moves down energy levels and moves closer to the nucleus they emit EM radiation

Question 2

How does nuclear decay generate EM waves?

Answer 2

• unstable nucleus causes nuclear decay
• high E gamma rays emitted

Question 3

Where do gamma rays originate from?

Answer 3

gamma rays originate from changes in the nucleus of an atom

Question 4

How are radio waves generated?

Answer 4

1. Radio waves can be produced by oscillations (oscillating electrons) in electrical circuits
2. Alternating current flows in the transmitting aerial
3. This causes oscillating electric and magnetic fields - generates an EM wave with same frequency as wave in electrical signal
4. E in the radio wave cause the electrons in the receiving aerial to start oscillating

Question 5

What may happen when radio waves are absorbed?

Answer 5

when radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself, so radio wave can themselves induce oscillations in an electrical circuit

Question 6

What effect can UV waves, X-rays and gamma rays have on the human body and what do these effects depend on?

Answer 6

• can have hazardous effect on human body tissue
• the effect depend on the type of radiation an the size of the dose

Question 7

What sort of waves are harmful to us?

Answer 7

• low frequency and low energy waves are not harmful to us
• high frequency and high energy harmful to humans - ionising radiation

Question 8

What are radiation doses?

Answer 8

• radiations doses (in sieverts) is a measure of the risk of harm resulting from an exposure of the human body to radiation
• 1000 millisieverts (mSv) = 1 sievert (Sv)

Question 9

Risk of X-rays and gamma rays:

Answer 9

• ionising radiation the can cause mutation of genes causing cells to uncontrollably divide therefore, causing cancer
  
  • ionise (lose electrons) - unwanted chemical reaction
• can damage surface of eyes - damages protein of lens, parts of the eye can be burnt

Question 10

Risks of UV waves:

Answer 10

• causes skin to age prematurely
  
  • can damage DNA causing mutations —> uncontrolled cell division —> skin cancer
• increases risk of skin cancer