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Physics > Chapter 12 And 13 -Using Waves And Light Waves > Flashcards

Chapter 12 And 13 -Using Waves And Light Waves Flashcards

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1
Q

What happens when wavelength increases

A

Frequency decreases

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2
Q

Name the 7 types of em waves in order of short to long wavelength

A

Gamma rays, X-Ray’s, ultraviolet,visible light, infra red, microwaves , radio waves

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3
Q

Harmful effects of microwaves

A

Can penetrate all body tissues and are absorbed by cytoplasm of living cells.
Causes body to overheat, if temperature increases too much body cells may die

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4
Q

Harmful effect of infra red waves

A

Over exposure can burn the skin

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5
Q

Harmful effects of ultra violet waves

A

Can be dangerous to our bodies. Much of the Suns ultraviolet rays are absorbed by the ozone layer.
If our bodies receive too much of this light skin can burn (sunburn) - can develop into skin cancer.
Too much uv waves an damage the human retina and can cause blindness

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6
Q

Harmful effects of x Ray’s waves

A

Can cause cancer if over exposed due to cell damage

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7
Q

Harmful effects of gamma rays

A

Cells can be destroyed or mutated

Can cause cancer

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8
Q

6 properties of EM waves

A
  1. All are transverse waves
  2. Transfer energy from one place to another
  3. Can travel through a vacuum
  4. Travel at the same speed.
  5. Consist of oscillating electric and magnetic fields
  6. Can be reflected, refracted and diffracted
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9
Q

Uses of radio waves

A

Radio transmitters

Tv transmitters

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10
Q

Uses of microwaves

A

Microwaves
Ovens
Mobile phone communication
Satellite

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11
Q

Uses of infra red waves

A

Infra red cookers and heaters
Tv and stereo remote controls
Night vision
IR cameras - detect cancer

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12
Q

Uses of visible light

A 
Safety clothing
Lasers - barcode scanners, CD rooms, optical fibres, military for guiding missiles 
Telecommunication 
Sensors 
Endoscopes
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13
Q

Uses of UV waves

A

Florescent tubes
UV scanning lamps
Washing powder

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14
Q

Uses of X Ray’s

A

X-radiography to observe the internal structure of objects

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15
Q

Uses of gamma rays

A

Sterilise food and medical objects

Cancer treatment

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16
Q

What do digital signals do

A

Converts info into binary code (0 and 1)

Converted into electrical pulses that are sent down a telephone line

17
Q

What do analogue signals do

A

Info is converted into electrical signals/ currents that vary continually
Signals are amplified and sent into a loud speaker

18
Q

4 advantages of digital signals

A
  1. All signals become weaker in transmission - needed to be amplified / regenerated
  2. Regeneration in digital signals makes a clean copy of original. In analogue the background noise is also amplified causing original to be drowned out or include errors when info is carried
  3. Digital systems are easier to design and build
  4. Digital systems deal with data that is easy to process
19
Q

Why are tv and radio broadcasted with digital signals nowadays

A

Takes a wide range of frequencies to broadcast analogue signals
Using digital means more programmes can be broadcasted over the same frequenseies

20
Q

What is optical fibre communication

A

Extremely pure glass is used to transmit infra red and light waves carrying large amounts of info and data
The light is continually reflected (total internal reflection ) along the fibre and is very secure

21
Q

What is cataract

A

When an eye becomes cloudy you cannot see out of it due to light not being able to enter the eye correctly
Now you can remove the damaged part and replace it with a clear plastic that will allow light to enter the eye

22
Q

Define luminous objects

A

Objects that emit light e.g. The sun

23
Q

Define non luminous objects

A

Objects that reflect light e.g. A book

24
Q

How does a periscope work

A

Uses two mirrors to change the direction of Ray’s of light
Rays from the mirror stake first mirror at angle of 45 degrees to the normals
The rays are reflected 45 degrees to the normal and are turned through an angle of 90 degrees.
Changing the direction of Ray’s of light in this way allows an observer to use a periscope to see over and around objects

25
Q

Properties of an image in a plane mirror

A

Image is a far behind the mirror as the object is infront.
Image is same size as the object
Image is virtual, cannot be produced on a screen
Image is laterally inverted / reversed
Image is upright

26
Q

What happens when a ray of light crosses a boundary of a different medium

A

If it enters a denser medium it will slow down causing the Ray to change direction and it is refracted towards the normal
If it enters a less dense medium it will do the opposite

27
Q

How do we see images in a mirror

A

Image is formed as Ray’s of light from an object hit the mirror
These rays are reflected back into eyes and brain interprets it

28
Q

Define virtual

A

Image in a plane mirror is a virtual image and the same size as the object

29
Q

What causes the dispersal in a prism with a rainbow

A
  • when each of the light colours have a different wavelength and speed in the medium
  • all colours have the same speed in a vacuum
  • when light enters the glass the different coloured lights slow down and are refracted
  • as each colour of light slows down a specific amount of the colours will be refracted though different angles
30
Q

What’s smells law

A

That the refractive index of a medium can be calculated from the angles of incidence and refraction
N = sin i
—–
Sin r

31
Q

What is total internal reflection

A

Can only Oxus when a ray of light travels from a medium with higher refractive index and the angle of incidence is greater than the critical angle

32
Q

What is an optical fibre

A

A thin rod of high quality glass
Very little light is absorbed by this glass
Light gets in at one end does repeated internal refraction and emerges at the other end
Works when fibre emerges at other end

33
Q

What is a real image

A

E.g. A movie on a cinema screen

Formed by real rays that meet at a point and can be projected onto a screen

34
Q

What is a virtual image

A

E.g. In a mirror

Formed by imaginary rays and cannot be projected onto a screen

Physics (6 decks)

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