EM Waves And Their Uses Flashcards

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1
Q

What type of waves are used for communication to and from satellites, including satellite TV signals and satellite phones?

A

microwaves

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2
Q

Why are microwaves preferred for satellite communication?

A

they can easily pass through the Earth’s watery atmosphere

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3
Q

Describe the process of satellite TV signal transmission and reception.

A

-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.

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4
Q

What type of waves are used in microwave ovens?

A

microwaves

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5
Q

How do microwaves interact with water molecules in food?

A

-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.

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6
Q

What type of radiation is emitted by all objects?

A

infrared (IR) radiation

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7
Q

How are infrared cameras used to detect and monitor temperature?

A

-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.

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8
Q

How does absorbing infrared radiation affect the temperature of objects?

A

Absorbing IR radiation causes objects to get hotter as the absorbed energy increases their temperature.

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9
Q

How can infrared radiation be utilised for cooking food?

A

-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

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10
Q

How do electric heaters utilise infrared radiation to heat a room?
what happens to objects and air in the room as a result?

A

-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

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11
Q

What are optical fibres?

A

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.

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12
Q

How do optical fibers work?

A

Optical fibers work due to reflection-light rays are bounced back and forth within the fiber until they reach the end.

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13
Q

Why is visible light used in optical fibers?

A

it can be refracted enough to remain in a narrow fiber.

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14
Q

What are the advantages of using light in optical fibers for data transmission?

A

Light is not easily absorbed or scattered as it travels along a fiber, making it an efficient medium for data transmission.

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15
Q

What is fluorescence?

A

-a property of certain chemicals where ultraviolet (UV) radiation is absorbed and visible light is emitted
-this makes fluorescent colors appear very bright

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16
Q

How do fluorescent lights work?

A

-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.

17
Q

What is the purpose of security pens?

A

-Security pens are used to mark property with invisible ink that fluoresces under UV light.
-This helps identify stolen property.

18
Q

How can ultraviolet (UV) radiation help with suntanning?

A

-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)

19
Q

How are X-rays used in hospitals?

A

Radiographers in hospitals use X-rays to take ‘photographs’ of people to detect broken bones and other internal issues

20
Q

What property of X-rays allows radiographers to create images of bones and other dense materials?

A

-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

21
Q

How are X-rays and gamma rays utilised in the treatment of cancer patients?

A

-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.