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Physics > Waves > Flashcards

Waves Flashcards

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1
Q

What is Wavelength?

A

Distance from one peak to the next

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2
Q

What is Frequency?

A
  • How many complete waves there are per second passing a certain point
  • Measured in hertz
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3
Q

What is Amplitude?

A

Height of the wave from rest to crest

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4
Q

What is the Speed?

A

How fast the wave goes

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5
Q

What is the Period?

A

The time (s) it takes for 1 complete wave to pass a point

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6
Q

Wave speed =

A

Frequency x Wavelength

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7
Q

What are Examples of Transverse Waves?

A
  • Light & EM waves
  • Waves on strings
  • Ripples on water
  • Slinky spring going up & down
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8
Q

What are Examples of Longitudinal Waves?

A
  • Sound & ultrasound
  • Shock waves
  • Slinky spring when push the end
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9
Q

Where are the Vibrations in Transverse Waves?

A

At 90 degrees to direction energy is transferred by wave

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10
Q

Where are the Vibrations in Longitudinal Waves?

A

Along same direction as wave transfers energy

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11
Q

What can Sound Waves make things do and give an example?

A
  • Make things vibrate & move

* E.g. loud bangs can start avalanches

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12
Q

What can Waves be used as Signals to do and give an example?

A
  • Used as signals to transfer info from one place to another
  • E.g. light in optic fibres, radio waves travelling through air
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13
Q

What can All Waves do?

A
  • Carry & transfer energy in direction they’re travelling
  • Microwaves in oven make things hot, their energy transferred to the food your cooking
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14
Q

What are Wavefronts?

A

Imaginary planes cut across all waves, connecting points on adjacent waves that are vibrating together

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15
Q

What is the Doppler Effect?

A
  • Makes waves appear longer or shorter
  • Frequency of source moving towards you seem higher, wavelength seem shorter
  • Frequency of source moving away from you seem lower, wavelength seem longer
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16
Q

What are the Electromagnetic Waves in order of increasing frequency and decreasing wavelength?

A
  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
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17
Q

What are all types of Electromagnetic waves and what do they all do?

A
  • Transverse waves

* Travel at same speed through free space

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18
Q

What are Radio Waves used for and what is the Process?

A
  • Tv and FM radio broadcasting

* Must be in direct sight of transmitter to get reception

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19
Q

What are Microwaves used for and what is the Process?

A
  • Satellite communication
  • Mobile phone calls from phone to nearest transmitter
  • Cooking, microwaves absorbed by water molecules in food, penetrate few cm into food then absorbed, energy conducted to other part of food
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20
Q

What are Infrared Radiation used for?

A
  • Electrical heaters

* Grills to cook food

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21
Q

What is Visible Light used for and what is the Process?

A
  • Communication using optical fibres, carrying data over long distances as pulses of light - phones
  • Photography, by varying aperture & shutter speed can capture as much light as you want
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22
Q

How do Optical Fibres work in Visible Light?

A
  • Bounce waves off sides of narrow core

* Light enters fibre at one end, reflected until emerges at other end

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23
Q

What is Ultraviolet used for?

A

Fluorescent lights use UV to emit visible light

24
Q

What are X-Rays used for and what is the Process?

A
  • View internal structure of objects, materials, bodies

* X-ray directed through object/body onto detector plate

25
Q

What are Gamma Rays used for and what is the Process?

A
  • Sterilise medical instruments by killing all microbes

* Sterilise food by killing microbes so fresher for longer

26
Q

How are X-Rays harmful?

A

Exposure to X-rays can cause mutations leading to cancer

27
Q

What Electromagnetic radiation are usually more Dangerous?

A

Higher frequency - more energy so generally more harmful

28
Q

How are Microwaves harmful and how can you Prevent this harm?

A
  • Internal heating - heat human body tissue

* Prevent - microwave ovens need shielding

29
Q

How are Infrared harmful and how can you Prevent this harm?

A
  • Skin burns

* Prevent - Use insulating materials

30
Q

How are Ultraviolet harmful and how can you Prevent this harm?

A
  • Damage surface cells -blindness , cell mutation/destruction, cancer
  • Prevent - wear sun cream, stay out of strong sunlight
31
Q

How are Gamma harmful and how can you Prevent this harm?

A
  • Ionising, a lot of energy
  • Penetrate further into body
  • Cell mutation/destruction - tissue damage, cancer
  • Prevent - exposure time short, kept in lead lines boxes when not using
32
Q

Angle of Incidence =

A

Angle of reflection

33
Q

What is Diffuse Reflection?

A

Light reflects from uneven surface, light reflects of at all different angles = diffuse reflection

34
Q

What is Clear Reflection?

A

Light reflects from even surface, all reflected at same angle = clear reflection

35
Q

What is the Normal line?

A

Imaginary line that’s perpendicular to the surface at point of incidence

36
Q

What is the Angle of Incidence?

A

Angle between the incoming wave and normal

37
Q

What is the Angle of Reflection?

A

Angle between reflected wave and normal

38
Q

How are Virtual Images Formed?

A

Light rays bouncing off object onto mirror are diverging, light from object appears to be coming from different place

39
Q

How can Waves be Refracted?

A
  • Wave hits boundary face on - slows down, carries on in same direction
  • Wave meet at different medium at angle, hits denser later first then slows down, carries on at first - faster speed, wave changes direction = refracted
40
Q

Why do Waves travel at different Speeds?

A
  • Have different densities
  • EM waves = slowly in denser media
  • Sound waves = faster in denser substances
41
Q

How do you draw a Ray Diagram for a Refracted Wave?

A
  • Draw boundary (line) between 2 materials & normal
  • Draw incident ray - meets normal at boundary
  • Between Ray & normal = angle of incidence
  • Refracted Ray on other side of boundary - denser = bends towards normal
  • Between refracted Ray & normal = angle of refraction (smaller)
42
Q

Explain how Rays passing through a glass box are Refracted Twice?

A
  • Light ray at angle into block, light is reflected, most light goes through glass & refracted
  • Trace incident & emergent rays onto paper
  • Light passes from air to block(denser), bends towards normal(because slows down)
  • Light to boundary on other side, speeds up because less dense, bends away from normal
  • Light ray travel in same direction it was to begin with - refracted to normal & back again by same amount
43
Q

What happens if you shine White Light into a Triangular Prism?

A
  • Different wavelengths of light refract by different amounts
  • White light goes into different colours as into prism - rainbow effect
44
Q

Refractive Index (n) =

A

Speed of light in vacuum (c) / speed of light in that material (v)

45
Q

n =

A

Sin i / Sin r

46
Q

What does it mean if the angle of incidence is Less than Critical Angle?

A

Most light passes out but a little bit is internally reflected

47
Q

What does it mean if the angle of incidence is Equal to Critical Angle?

A

Emerging Ray comes out along surface - a lot of internal reflection

48
Q

What does it mean if the angle of incidence is Greater than Critical Angle?

A

No light comes out - all internally reflected - total internal reflection

49
Q

Sin C =

A

1 / n

50
Q

How do Optical Fibres use Total Internal Reflection?

A
  • Have central core w/ lower refractive index
  • Core of fibre narrow so light hit core-cladding boundary at angles above C
  • Light always totally internally reflected
51
Q

How do Prisms use Total Internal Reflection?

A
  • Light onto prism, totally internally reflected at 90 degree
  • Go to another prism lower down & totally internally reflected
  • Ray travelling parallel to initial path
52
Q

What are Sound Waves, how do they Act and what are they Caused by?

A
  • Longitudinal waves
  • Caused by vibrating objects
  • Vibrations through surrounding medium as compressions
  • Denser medium = faster sound
  • Reflected by hard flat surfaces
  • Refract as enter different media
53
Q

How can you Display Sound Waves and what does it tell you?

A
  • Oscilloscope- displays microphone signal as trace on a screen
  • Tells you If loud/quiet, high/low pitched, compare frequency of waves
  • High frequency = high pitched
54
Q

What does it mean if the Sound wave has a Greater Amplitude?

A
  • Carries more energy

* It will be louder

55
Q

What does the horizontal axis on oscilloscope tell you?

A

Time

56
Q

If 1 cycle crosses 20 division, what is the Period, if time division is set to 0.00001s?

A

20 x 0.00001s = 0.0002s

57
Q

How do you use an Oscilloscope to Measure the Speed of Sound?

A
  • Attach single generator to speaker - generate sound with specific frequency
  • 2 microphones & oscilloscope
  • Move microphones one wavelength apart
  • Wavelength of sound waves generated = measure distance between microphones
  • Use wave speed = freq x wavelength

Physics (7 decks)

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