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P1 topic 2
The electromagnetic spectrum
| Question | Answer |
|---|---|
| What do all electromagnetic waves have in common? | They all travel at 300,000km/s in a vacuum, and they are all transverse |
| What is the EM spectrum, in increasing wavelength and decreasing frequency? | Gamma rays X-rays Ultra-violet rays Visible light Infrared Microwaves Radiowaves |
| TRUE OR FALSE: the EM spectrum is continuous. | TRUE: the spectrum is continuous so all values of wavelength are possible |
| Describe in terms of frequency, the dangers of electromagnetic waves. | The greater the frequency of an EM wave, the more energy it transfers, therefore the more hazardous it is |
| What are the dangers and uses of microwaves? | DANGERS: can heat water, so since 70% of our bodies are made up of water there is a risk of internal heating of body cells USES: satellite transmission, e.g. they can carry TV signals. They also vibrate & heat up molecules so they're used in cooking |
| What are the dangers and uses of infrared? | DANGERS: our skin absorbs IR radiation which we feel as heat, and in large doses it can damage our cells and lead to skin burns USES: TV remote controls and cooking. Since all warm objects give off heat as IR radiation it can be used in thermal imaging |
| What are the dangers and uses of ultraviolet? | DANGERS: can damage surface cells leading to cancer. Can damage our eyes, leading to cataracts which is a clouding of the lens USES: Fluorescent lamps, detecting forged bank notes, disinfecting water |
| What are the dangers and uses of x-rays? | DANGERS: can be absorbed by the body and can cause mutations in DNA leading to cancer USES: observing the internal structure of objects, medical x-rays |
| What are the dangers and uses of gamma rays? | DANGERS: can be absorbed by the body and can cause mutations in DNA leading to cancer USES: can kill cells so used to sterilize food and kill cancer (radiotherapy). Can also detect cancer |
| What are the uses of visible light? | Vision, photography and illumination |
| What are the uses of radio waves? | Broadcasting, satellite transmissions (can carry TV signals), communications |
| How can gamma rays detect cancer? | Can detect cancer- a radioactive chemical that emits gamma rays is injected into blood, the chemical collects inside cancer cells and a scanner locates the cancer by finding the source of the gamma rays. |
| What is a radioactive source? | Materials that emit ionising radiation all the time |
| What is ionising radiation and what are 3 examples? | Radiation or certain types of high-energy particles that remove electrons from atoms to form ions. Alpha, beta and gamma are types of ionising radiation and all transfer energy from the radioactive material to their surroundings |
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