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Physics 1 > The Electromagnetic Spectrum > Flashcards

The Electromagnetic Spectrum Flashcards

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1
Q

What is white light made up of?

A

White light is made up of different colours. These colours can be dispersed into a spectrum using a prism.

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2
Q

When did William Herschel discover infrared waves?

A

In 1800.

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3
Q

How did William Herschel discover infrared waves?

A

He was investigating the temperature of the visible spectrum. He found that the hottest temperatures were beyond the red end of the spectrum, where there is no visible light. This is known as the infrared region. Infrared waves have a longer wavelength than red light.

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4
Q

When did Johann Ritter discover ultraviolet waves?

A

In 1801.

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5
Q

How did Johann Ritter discover ultraviolet waves?

A

He was experimenting with silver chloride used in photography. The rate of reaction was highest beyond the violet end of the visible spectrum. Ultraviolet waves have a shorter wavelength than violet light.

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6
Q

What is the big problem with ultraviolet waves from the Sun?

A

Ultraviolet waves from the Sun are harmful. They will damage skin cells and eyes. The most common form of this damage is sun burn, but long exposure can cause skin cancer.

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7
Q

What are the three types of ultraviolet waves?

A
  • UV-A
  • UV-B
  • UV-C
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8
Q

Which ultraviolet wave is the shortest wavelength?

A

UV-C waves have the shortest wavelength and cause the most damage.

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9
Q

What are ultraviolet, visible light and infrared all a part of?

A

Ultraviolet, visible light and infrared are all part of a family of waves know as the electromagnetic spectrum.

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10
Q

What are all electromagnetic waves

A

All electromagnetic waves are transverse and travel at the same speed in a vaccuum (300,000,000 m/s).

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11
Q

What can EM waves do?

A
  • can transfer energy
  • can be reflected, refracted and diffracted
  • obey the wave equation:
    wave speed = wavelength x frequency
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12
Q

What is the order of decreasing wavelength and increasing frequency?

A 
radio waves,
microwaves, 
infrared radiation,
visible light,
ultraviolet, 
x-ray,
gamma-rays
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13
Q

What do EM waves consist of?

A

EM waves consist of an oscillating electric field combined with an oscillating magnetic field. The who oscillating fields are at right angles to each other and to the direction of wave travel, so EM waves are transverse.

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14
Q

How long are the wavelengths of EM waves?

A

The wavelength of EM waves vaaries from about the size of the nucleus of at atom (10 to the -15m) up to several kilometres (10 to 3m).

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15
Q

How are radio waves produced and detected?

A

Radio waves are produced and detected by aerials.

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16
Q

What are radio waves used to do?

A

Radio waves are used to broadcast television and radio programmes. They are also used by emergency services for communication.

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17
Q

What are microwaves?

A

Microwaves are very high frequency (short wavelength) radio waves.

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18
Q

What are microwaves used for?

A

Microwaves are used to cook food in a microwave oven. Microwaves are also used for mobile-phone communication.

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19
Q

How do microwaves work in a microwave oven?

A

The microwaves are absorbed by water and fat in the food and the energy becomes heat.

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20
Q

What are sky waves?

A

Medium-frequency radio waves (MW) can reflect off the ionosphere to communicate long distances. These reflected waves are called sky waves.

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21
Q

Where do high frequency radio waves travel?

A

High frequency radio waves (and microwaves) travel in straight lines to satellites.

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22
Q

Why do mobile-phone networks use satellites?

A

Mobile-phone networks use satellites to transmit communications around the world at high speeds.

23
Q

What do all objects with a temperature above absolute zero (-273 degrees Celsius) do?

A

All objects with a temperature above the absolute zero (-273 degrees Celsius) emit infrared waves. The higher the temperature, the more infrared waves are emitted.

24
Q

What are the uses of infrared waves?

A

Infrared waves are used in cooking, in the grill, toaster and oven. Rescue services use infrared cameras to find bodies under rubble. Infrared waves are also used for short-range communication, such as in remote control or a cordless computer mouse.

25
Q

What are the uses of visible light?

A

Visible light is used in photography and in lighting in our homes and streets.

26
Q

How do ultraviolet lamps produce ultraviolet light?

A

Ultraviolet lamps produce ultraviolet light when mercury vapour conducts electricity.

27
Q

What are the uses of UV?

A

Some security markings can only be seen under UV light, such as the markings on bank notes. UV is also used to sterilise water as it kills bacteria.

28
Q

What are photographs taken with infrared called?

A

Photographs taken with infrared are called thermographs.

29
Q

What are both visible light and infrared waves transmitted along?

A

Both visible light and infrared waves are transmitted along optical fibres for communications.

30
Q

What happens if you increase the angle of incidence as light rays leave a more dense material?

A

If you increase the angle of incidence as light rays leave a more dense material, the angle of refraction away from the normal increases.

31
Q

What is the critical angle?

A

Eventually it will become refracted along the boundary and there will be some internal reflection. This is the critical angle.

32
Q

What happens at even greater angles?

A

At even greater angles, the light undergoes total internal reflection.

33
Q

How are X-rays produced?

A

X-rays are produced when fast-moving electrons hit a metal plate.

34
Q

What are the uses of X-rays?

A
  • airport security scanners
  • medical X-rays to detect the condition of bones and teeth
  • to detect unwanted pieces of metal in machinery.
35
Q

How are gamma rays produced?

A

Gamma rays are produced by radioactive materials.

36
Q

What are the uses of gamma rays?

A

Gamma rays kill bacteria so they are used to sterilise food and medical instruments. Gamma rays are also used in radiotherapy to treat cancers.

37
Q

What happens in an X-ray machine?

A

In an X-ray machine, a very high voltage is applied between the electrodes. The electrons are accelerated and hit a tungsten target. The fast-moving electrons collide with tungsten atoms, causing them to emit X-rays.

38
Q

What do radio waves do?

A

Radio waves are safe because they do not produce ionisation.

39
Q

What do microwaves do?

A

Microwaves cause internal heating of the body cells.

40
Q

What does infrared radiation do?

A

Infrared radiation can cause skin burns,

41
Q

What does visible light do?

A

Intense visible light can cause permanent damage to the retina.

42
Q

What does ultraviolet do?

A
  • Intense ultraviolet light damages skin (surface) cells
  • it can trigger skin cancer
  • it can cause eye conditions such as cataracts
  • it can destroy proteins in the eye lens
43
Q

What do X-rays and gamma rays do?

A
  • X-rays and gamma rays can damage the DNA of a cell
  • they can also mutate cells
  • they can also trigger cancer
44
Q

What do atoms consist of?

A

Atoms consist of tiny, positively charge nucleus surrounding by negatively charge electron.

45
Q

What is radioactivity?

A

Some atoms have unstable unclei, which breaks down, releasing energy in the form of alpha particles, beta particles or gamma rays. This is called radioactivity.

46
Q

When were X-rays and radioactivity discovered?

A

X-rays and radioactivity were discovered at the end of the 19th century.

47
Q

What is ionisation?

A

All types of radiation transfer some of their energy to the atoms of the material they are passing through. When this happens, electrons can get knocked off the atom to form a positive ion. This is known as ionisation.

48
Q

How are negative ions formed?

A

Negative ions are formed when an atoms gains electrons by ionisation.

49
Q

How can ionising radiation from radioactive sources be detected?

A

Ionising radiation from radioactive sources can be detected using a Geiger-Muller tube.

50
Q

What happens in a Geiger-Muller tube?

A

When an alpha or beta particle enters the tube, it ionises the gas inside the rube. This produces a pulse of electrical charge, which is detected by the counter attached to the GM tube. Each click or count represents one particle being detected.

51
Q

What is ioning radiation?

A

Radiation that can knock electrons out of atoms

52
Q

Which type of radiation is the least penetrating?

A

Alpha.

53
Q

Which type of radiation travels the furthest from its source in air?

A

Gamma.

Physics 1 (13 decks)

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