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Physics > Topic 5: The Electromagnetic Spectrum > Flashcards

Topic 5: The Electromagnetic Spectrum Flashcards

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1
Q

What is a ray diagram?

A

It is a way of modelling what happens when light is relefledt or refracted.

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2
Q

What are the angles of incident and angle of refraction?

A

These are measured firm the normal to see how much refraction has occurred.

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3
Q

What is the law of reflection?

A

When waves are reflected, the angle of reflection is equal to that of the angle of incidence.

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4
Q

Do different materials affect the speed at which light travels?

A

Light travels at different speeds in different materials. It travels faster in air then water then glass.

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5
Q

When does light bend towards or away from the normal?

A

Light bends towards the normal if it goes through a medium where it travels more slowly. It bends away from the normal of it goes through a medium where it travels faster.

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6
Q

What is total internal reflection?

A

The reflection of a light ray inside a medium such as glass or water when it reaches the interface. Total internal reflection only occurs when the angle of incidence inside the material is bigger than the the critical angle.

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7
Q

What is the critical angle?

A

Beyond a certain angle all the waves reflect back into the glass this creates total internal reflection. The angle that this happens at is the critical angle.

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8
Q

How does total internal reflection occur?

A

When light passes through a different medium it with a small angle of incidence most of the light passes through the interface but a little is reflected. As the angle of incidence increase the angle of refraction also increases until the refracted light also passes along the interface. If the angle is refracted further it is reflected inside the glass.

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9
Q

How do you see luminous colours?

A

When light from them enters your eyes. You see non luminous objects because they reflect light.

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10
Q

What is the difference between diffuse and speculate defection?

A

Diffuse reflection: when reflected light is scattered in all directions due to a rough surface.

Speculate reflection: when smooth surfaces such as mirrors reflect light evenly.

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11
Q

How can white light be split up into the different colours of the rainbow?

A

Using a prism separates the different frequencies of light into different colours of the rainbow.

White light can be split up into the visible spectrum.

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12
Q

Why does a yellow object look yellow or a white object look white?

A

Because when a white light hits a coloured surface some of the colours that make it up are absorbed. E.g a yellow object reflects yellow light and absorbs all the other colours. White objects reflect all colours too look white.

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13
Q

What is filter?

A

Filters are pieces of transparent material that absorb some of the colours in white light. E,g a blue filter transmits blue and absorbs all the other colours in the visible spectrum.

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14
Q

What is the visible spectrum and what is visible light?

A

visible light: Electromagnetic waves that can be detected by the human eye.

Visible spectrum: the 7 colours that make up white light.

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15
Q

What is a lens?

A

A transparent material shaped to refract light in a particular way.

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16
Q

How is the power of a lens defined?

A

The power of a lens describes how much it bends light and passes through it. A more powerful lens is curves more and bends the light more.

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17
Q

What is converging lens?

A

It is fatter in the middle and thinner at the edges. It makes parallel rays of light converge at the focal point.

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18
Q

What is a diverging lens?

A

This is thinner in the middle than at the edges. The focal point is the point from which the rays seem to be coming after passing through the lens.

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19
Q

What is a real image?

A

An image that can be projected on to a screen. They can only be formed when light rays converge/come together. Real image is normally on the other side of the lens upside down and smaller.

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20
Q

What does a converging lens do?

A

The kind of image formed depends on a where the object is. It can be used to focus rays of light onto a screen.

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21
Q

What is a virtual image and how is it formed?

A

Formed when an object is close to a converging lens. They cannot be projected onto a screen. The image appears to be on the same side of the lens as the object and is upright and magnified. A magnifying glass does this and is a converging lens.

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22
Q

What kind of image do diverging lenses form?

A

They form virtual images that are the same way up and much smaller and closer to the lens than the object.

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23
Q

What kind of image do both converging and diverging lenses form and what is the difference?

A

They both form virtual images. But diverging virtual images are closer to the lens, and smaller but still on the same side.

Converging virtual images are on the same side but behind the object and are magnified.

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24
Q

How do we see objects?

A

When light travels from a source and is reflected by an object into our eyes. The light transfers energy from the source into our eyes. Light is a type of electromagnetic wave.

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25
Q

What are the different frequencies of light and how does this affect the way we see things?

A

Our eyes can detect different frequencies of light and we refer to these as visible light. Different frequencies cause us to see different colours. Lower frequencies appear more red and higher frequencies appear more violet.

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26
Q

What is frequency higher than violet called?

A

Ultraviolet (UV)

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27
Q

What is the frequency lower than red called?

A

Infra red

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28
Q

How fast do electromagnetic waves travel through a vacuum?

A

They all travel at the same speed which is 3x10 to the power of 8 m/s or 300,000,000 m/s.

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29
Q

What do all electro magnetic waves have in common?

A

They are all transverse (so their vibrations are at right angles to which the ergo is being transferred by the wave.)

All travel at the same speed.

30
Q

What type of energy do all objects emit?

A

All objects emit infra red radiation. The hotter the object the more energy it emits. We can feel the effects of infrared radiation when energy is transferred form the sun to our skin.

31
Q

How was infrared discovered?

A

Discovered by William Herschel.
He put dark colour filters of his telescope to help him observe the sun safely. He noticed different colour filters heated up his telescope at different extents and wondered if different colours had ‘different amount of heat’
To test this idea he used a prism to split sunlight into the colours of the spectrum and then put a thermometer in each of the colours in turn. He also measured the temperature just beyond the red end of the spectrum where the temperature was higher.

32
Q

What are the 7 colours of the rainbow?

A

Red, orange, yellow, green, blue, indigo, violet.

Richard Of York Gave Battle In Vain

33
Q

What colours are below the frequency of red?

A

Infra red, microwave and radio waves

These have longer wavelengths.

34
Q

Why can we only see visible light?

A

If the frequency is above or below the visible spectrum human eyes cannot see it.

35
Q

What frequencies are higher than violet?

A

Ultra violet, x rays and gamma rays.

These have shorter wavelengths.

36
Q

Describe the wavelengths and frequencies of the electromagnetic spectrum:

A

The spectrum is continuous, so all values of frequency are possible. High frequency waves have a shorter wavelength and lower frequencies have a longer wavelength.

37
Q

Why do telescopes used curves mirrors?

A

Most telescopes use curved mirrors to focus the electromagnetic radiation onto a central sensor. The type of material used for the mirror and and the size of the telescope depend on the type of radiation being studied.

38
Q

Does radiation exist in out atmosphere?

A

Yes electromagnetic radiation does. Stars and other space objects can emit energy at all wavelengths. Astronomers need to use specialised telescopes for different types of radiation. This is because different materials affect electromagnetic waves depending on their wavelength. E.g some waves pass through our atmosphere while others are absorbed.

39
Q

What are the uses of infrared radiation?

A
  • communication at short ranges (e.g computers in the same room or TV to its remote control).
  • information sent along optical fibres.
  • a grill or toaster transfers energy to food by infrared radiation.
  • security systems have sensors that can detect infrared radiation emitted by intruders.
40
Q

What are the uses of microwaves?

A
  • communication and satellite transmissions, including mobile phone transmissions.
  • in a microwave oven microwaves transfer energy to food to heat it up.
41
Q

What are the uses of radio waves?

A
  • transmitting radio broadcasts and TV programmes as well as other communication.
  • controllers on the ground communicate with spacecrafts using radio waves.
42
Q

How are radio waves produced?

A

Produced by oscillations (variations in current and voltage) in electrical circuits.

43
Q

How are radio waves received?

A

A metal rod or wire can be used as an aerial to receive the radio wave. The radio waves are absorbed by the metal and cause oscillations in electrical currents connected to the aerial.

44
Q

What causes action if a wave?

A

Change in velocity

45
Q

Why are microwaves better than radio waves when sending waves out of our atmosphere?

A

Some frequencies of radio waves can be refracted by a layer in the atmosphere called the ionosphere. If radio waves reach the ionosphere at a particular angle they may be refracted enough to send them back towards Earth. Microwaves are nit refracted in the deaths atmosphere.

46
Q

What is the order of the electromagnetic spectrum?

A
  • gamma rays
  • x rays
  • ultraviolet
  • visible light
  • infrared
  • microwaves
  • radio waves
47
Q

What is an oscillation?

A

-

48
Q

How can the intensity of radio emitted increase?

A

The intensity (amount) increases when the temperature increases.

49
Q

How does the temperature affect the wavelength?

A

The higher the temperature the shorter the wavelength.

50
Q

How must a system stay at a constant temperature?

A

It must absorb the same amount of energy it emits/radiates.

51
Q

What must happen for the earths temperature to stay the same?

A

It must radiate energy into space at the same average rate it is absorbed.

52
Q

What sort of radiation does the Earth re-radiate from the sun?

A

It re-radiates this energy as infrared radiation, which can warm up the atmosphere.

53
Q

What is the green house affect?

A

Some gases on our atmosphere such as carbon dioxide naturally absorb some energy (being remitted from earth surface to space), keeping the earth at a higher temperature than if there was no atmosphere.

54
Q

What would happen is some green house gases were removed?

A

The atmosphere would be able to hold less energy and its temperature would decrease.

55
Q

Core practical investigating radiation method:

A

1-cover 4 or more boiling tubes in different materials (such as shiny silver, dull grey, dull black, shiny black.)

2-pout the same volume of hot water into each tube

3-Insert a bung with a thermometer in each tube. Measure the current temperature in each tube and record this and then start the stop watch.

4-record the temperature of the water in each tube every 2 minutes for 20 minutes.

56
Q

What is the core practical for investigating radiation?

A

Different types of surfaces affect how much energy is transferred by the radiation from different objects. You will investigate the the effect of different coloured surfaces on the amount of energy transferred by radiation from a tube of hot water.

57
Q

Compare ultraviolet radiation to visible light:

A

Ultraviolet radiation transfers more energy than visible light. It is absorbed by most of the same materials, including our skin.

Some materials absorb ultraviolet radiation and remit it as visible light. This is called fluorescence.

58
Q

Uses of ultraviolet light:

A
  • used to disinfect water by killing microbes init.

- Fluorescent marking only visible when ultra violet light shines on them.

59
Q

What can x rays do that visible light cannot? And what are the uses of x rays?

A

Pass through many materials that visible light cannot. Such as skin. They can pass through muscle and fat easily but bone absorbs them so this can therefore be used for medical purposes.e,g x rays

They can also be used to see the inside of meta, objects and inspect luggage in airport scanners.

60
Q

What are the uses of gamma rays?

A
  • transfer slot of energy so can kill cells.
  • used to sterilise food and surgical equipment by killing harmful microbes.
  • used to kill cancer cells in radio therapy.
  • can be used to detect cancer.
61
Q

How can gamma rays detect cancer?

A

A chemical that emits gamma rays is injected into the blood stream. The chemical is designed to collect inside cancer cells. A scanner then outside the body detects whee the gamma rays are being emitted from.

GAMMA RAYS CAN PASS THROUGH SLL MATERIALS IN THE BODY.

62
Q

How can microwaves be potentially harmful to us?

A

80% of the human body is water. Micro waves could potentially heat up our cells in out body. Mobile phone use microwaves but a different frequency that is less harmful.

63
Q

How can infrared radiation be harmful?

A

Used to heat things if exposed too much infra red can damage and destroy skin cells causing burns.

64
Q

How can ultraviolet (sunlight) be harmful?

A
  • cause sunburns and damage to DNA.

- to much exposure can lead to skin cancer.

65
Q

Why are gamma rays used when detecting and killing cancer cells?

A

Because they can pass through all materials.

66
Q

How can microwaves be damaging?

A

A certain microwave frequency can be used to heat water. This is used in microwave ovens. Harmful because a lot of our body is made from water so it could heat the cells inside our body.

67
Q

Why is microwave radiation from phones not harmful unlike microwave ovens?

A

Because it uses a different frequencies of microwave which does not prove to be harmful to our health.

68
Q

Why are high frequency waves more harmful than low frequency waves?

A

Because they carry more energy so are potentially more dangerous.

69
Q

How can we protect ourselves from ultraviolet radiation?

A
  • staying out of constant sunlight.
  • covering up with clothes and sun hats, sun glasses.
  • using cream with a high SPF factor.
  • skiers where special glasses to stop the ultraviolet radiation reflecting from the white snow into their eyes.
70
Q

How do gamma and X-rays cause harm to humans and why?

A

They have a higher frequency that ultraviolet radiation so transfer more energy. They are also able to penetrate the body. Excessive exposure can cause mutations and can kill cells and even cause cancer.

71
Q

How is electromagnetic radiation produced?

A

Produced by changes in electrons or the nuclei in atoms.

E.g when materials are heated changes in the arrangement of electrons can produce infra red radiation or visible light.
Changes in the nuclei of an atom can cause gamma radiation.

Physics (11 decks)

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