EM Waves And Their Uses Flashcards
What type of waves are used for communication to and from satellites, including satellite TV signals and satellite phones?
microwaves
Why are microwaves preferred for satellite communication?
they can easily pass through the Earth’s watery atmosphere
Describe the process of satellite TV signal transmission and reception.
-For satellite TV, the signal from a transmitter is transmitted into space and received by a satellite receiver dish orbiting thousands of kilometers above the Earth.
-The satellite then transmits the signal back to Earth, where it is received by a satellite dish on the ground.
-There is a slight time delay between the signal being sent and received due to the long distance the signal has to travel.
What type of waves are used in microwave ovens?
microwaves
How do microwaves interact with water molecules in food?
-In microwave ovens, microwaves penetrate up to a few centimeters into the food before being absorbed by water molecules.
-The absorbed microwaves transfer their energy to the water molecules, causing them to heat up.
-This heat is then transferred to the rest of the molecules in the food, quickly cooking it.
What type of radiation is emitted by all objects?
infrared (IR) radiation
How are infrared cameras used to detect and monitor temperature?
-Infrared cameras detect and monitor temperature by converting IR radiation into electrical signals, which are displayed on a screen as a picture.
-Hotter objects appear brighter in the image.
How does absorbing infrared radiation affect the temperature of objects?
Absorbing IR radiation causes objects to get hotter as the absorbed energy increases their temperature.
How can infrared radiation be utilised for cooking food?
-Food can be cooked using IR radiation, as the temperature of the food increases when it absorbs IR radiation
-e.g. when a toaster heats up food
How do electric heaters utilise infrared radiation to heat a room?
what happens to objects and air in the room as a result?
-Electric heaters emit infrared radiation when a current flows through a wire, heating objects and air in a room.
-The absorbed IR radiation transfers energy to the thermal energy stores of objects, increasing their temperature
What are optical fibres?
Optical fibers are thin glass or plastic fibers that can carry data, such as from telephones or computers, over long distances as pulses of visible light.
How do optical fibers work?
Optical fibers work due to reflection-light rays are bounced back and forth within the fiber until they reach the end.
Why is visible light used in optical fibers?
it can be refracted enough to remain in a narrow fiber.
What are the advantages of using light in optical fibers for data transmission?
Light is not easily absorbed or scattered as it travels along a fiber, making it an efficient medium for data transmission.
What is fluorescence?
-a property of certain chemicals where ultraviolet (UV) radiation is absorbed and visible light is emitted
-this makes fluorescent colors appear very bright
How do fluorescent lights work?
-Fluorescent lights generate UV radiation, which is absorbed and re-emitted as visible light by a layer of phosphor inside the bulb.
-They are energy-efficient and suitable for long-term use.
What is the purpose of security pens?
-Security pens are used to mark property with invisible ink that fluoresces under UV light.
-This helps identify stolen property.
How can ultraviolet (UV) radiation help with suntanning?
-Tanning salons use UV lamps to provide artificial suntans.
-overexposure to UV radiation can be dangerous (though fluorescent lights emit very little so they’re safe)
How are X-rays used in hospitals?
Radiographers in hospitals use X-rays to take ‘photographs’ of people to detect broken bones and other internal issues
What property of X-rays allows radiographers to create images of bones and other dense materials?
-X-rays pass easily through flesh but not through denser material like bones or metal
-The amount of radiation absorbed or not absorbed creates an X-ray image
How are X-rays and gamma rays utilised in the treatment of cancer patients?
-X-rays and gamma rays are used in radiotherapy to treat cancer
-High doses of these rays are carefully directed towards cancer cells to kill them while minimising damage to healthy cells.
