Electromagnetic Waves
- Created by: SamDavies
- Created on: 09-02-14 21:04
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- Electromagnetic Waves
- Radiowaves
- Uses
- Broadcasting
- TV and FM Radio broadcasting
- 10cm-10m
- To get reception, you have to be in direct sight of the transmitter
- Cannot diffract or go around hills; doesn't go far through tunnels
- TV and FM Radio broadcasting
- Communication
- Long-wave radio
- 1-10km
- Can be receieved halfway around the world due to diffraction
- bend around the surfaces of the Earth, and around hills, through tunnels etc.
- Can be receieved halfway around the world due to diffraction
- Short-wave radio
- 10-100m
- Can be receieved from a long distance
- due to the waves reflecting off the ionosphere
- Electrically charged layers in the Earth's upper atmosphere
- Long-wave radio
- Broadcasting
- Uses
- Microwaves
- Uses
- Cooking
- Microwaves are absorbed by the water molecules in the food
- They penetrate a few cm into the food before being absorbed
- The energy is then conducted or convected to other parts of the food
- They penetrate a few cm into the food before being absorbed
- Microwaves are absorbed by the water molecules in the food
- Satellite transmissions
- 1-10cm
- Use microwaves that move through the Earth's watery atmosphere without being absorbed
- For a satellite TV, the signal from the transmitter is transmitted to space
- There it is picked up on by a satellite receiver dish orbiting thousands of kilometers above the Earth
- The signal is then transmitted back down to Earth in different directions
- From that it is received from a satellite dish on the ground
- The signal is then transmitted back down to Earth in different directions
- There it is picked up on by a satellite receiver dish orbiting thousands of kilometers above the Earth
- Cooking
- Dangers
- Internal heating of body tissue
- Uses
- Infrared
- Dangers
- Skin burns
- Uses
- Heaters
- ALL objects give off IR - The hotter the object, the more IR it gives off
- Night-vision equipment
- Turns IR into electrical signals which is displayed on screen as a picture
- Allows things that would be otherwise hidden in the dark, e.g. criminals, to be seen
- remote controls for TVs
- short-range communications, for example between mobile phones
- Heaters
- Dangers
- Visible light
- Ultraviolet
- Uses
- UV is absorbed and light is emitted in fluorescent lighting
- Nearly all of the UV radiation is absorbed by a phosphor coating on the inside of the glass
- Fluorescent lights are more energy efficient than filament light bulbs
- UV is absorbed and light is emitted in fluorescent lighting
- Dangers
- Damage surface cells
- Blindness
- Cell mutations and cancer
- Due to UV radiation being ionising - able to knock electrons off atoms
- Safety precautions
- Wear sunscreen with UV filters
- Stay out of strong sunlight
- Sun burn/ skin cancer
- Uses
- X-Rays
- Uses
- View the internal structure of objects (like bodies
- Produce x-ray images
- X-ray radiation is directed through the body onto a detector plate
- X-rays pass easily through flesh but not through denser materials like bones or metal
- The brighter bits of the x-ray image is where less radiation can get through
- Airport security
- Dangers
- Cell mutation and cancer
- Safety precautions
- Lead aprons and shields
- Minimum exposure to the radiation
- Given off by stars
- Barium meal
- Drink of barium sulphate which will absorb the x-rays, so the patient's intestines will show up clearly on a x-ray image
- Uses
- Gamma Rays
- Uses
- Sterilising medical equipment
- Gamma rays kill the microbes
- Better than boiling plastic instruments as they will likely be damaged by the high temperatures
- Sterilising food
- By killing the microbes
- Keeps food fresher for longer without freezing it or cooking it or preserving it some other way
- Food is not radioactive afterwards - safe to eat
- Can kill cancer cells (radiotherapy)
- Sterilising medical equipment
- Dangers
- Cell mutation
- Tissue damage
- Cancer
- Strongly ionising and carry the most energy
- Penetrate further in the body
- Safety precautions
- Kept in a lead-lined box when not in use
- Minimum exposure time
- Protective clothing
- Uses
- Radiowaves
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