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Physics > Waves > Flashcards

Waves Flashcards

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1
Q

Waves

A

Transfer of energy through a medium caused by oscillation or vibration
-energy is tranferred not matter

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2
Q

Longitudinal waves

A
  • medium oscillates parallel to the direction of energy travel
  • caused by compressions and rarefactions of same medium
  • cant travel in vacuum as particals are needed so change of density
  • eg. Sound, mechanical waves (slinky/spring), deep water waves, earthquakes, AC
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3
Q

Transverse waves

A
  • field oscillates perpendicular to direction of energy transfer
  • caused by vibrations of field/medium
  • density is constant
  • can travel through medium
  • light, em waves,ripples on water
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4
Q

Human ear range- sound waves

A

20HZ-KHz

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5
Q

What is amplitude in sound measured in

A

Decibels

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6
Q

Ultrasound

A
  • frequency above 20khz

- used in sonograms(pregnany scans), echolocation, cleaning

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7
Q

Infrasound

A

-sound below 20Hz

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8
Q

Dangers of sound

A
  • xtremely loud sounds- extreme pressure changes- force on eardrum bsting it
  • exposure to loud sounds over long time- damage
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9
Q

How to prevent danger of sounds

A
  • ear protection
  • shorter time w/ loud sounds
  • positioning behind sound
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10
Q

Refraction

A

Wave changes direction due to change in soeed at boundry

-depends on refractive index

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11
Q

Plano

A

Flat one side

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12
Q

Double

A

Both sides

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13
Q

Convex

A

Wider middle

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14
Q

Concave

A

Smaller in middle

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15
Q

Focal point

A

Point at which parallel light rays (which have passed through a lens) converge

  • determined by shape and material of len
  • sharp images formed at focal point
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16
Q

Converging rays

A

-light rays focus on one point

17
Q

Diverging rays

A

-spread out as if from one point

18
Q

Frequency

A

How many waves pass a point per second

19
Q

Time period

A

How ong it takes for one complete osciallation or cycle

20
Q

Wavelength

A

Distance two neighboring peaks

21
Q

Amplitude

A

-maximum displacement of the vibration from rest

22
Q

High pitch

A
  • higher frequency

- same heught amplitude

23
Q

Higher volume

A

Higher amplitude

Same wavelength and frequency

24
Q

As wave speed increases

A

Bends away from normal

25
Q

What happens when a wave is absorbed

A
  • wave stops travelling
  • goes into but not through medium
  • energy is transferred to the material, causing the material’s energy store to increase
    • kinetic store- moves
    • internal energy stores-heat up or change state
    • chemical energy store- light waves photosynthesis
26
Q

Wave is transmitted

A

Wave continues moving through medium

  • wave may be changed- diffraction and rfraction
  • eg. Light through glass, sound through air
27
Q

Diffaction

A
  • waves spread out when passes through gap or round corner
  • narrower the gap/greater the wavelength- more the diffraction
  • only occurs if the gapsize is approx same as wavelength
  • wavelength, frequency and speed unchanged
28
Q

TIR

A

Total internal reflection

  • greater than critical angle- light reflects beack into medium
  • light must be traveling from a more optically dense medium into less optically dense medium (glass to air)
29
Q

At critical angle

A
  • emergent ray is perpendicular to normal

- moves along boundry

30
Q

Optical fibres

A
  • long thin rod of glass
  • uses tir to transfer info by llight
  • used medicine-endoscopy
  • communications- high speed data transfer
31
Q

Positives of optical fibres

A
  • high bandwidth-lots info per second
  • cheaper than copper
  • long distances without losses
32
Q

Negatives optical fibres

A
  • complex

- more fragile

33
Q

Telecoms- optical fibres

A
  • info sent at speed of light through binary code (turning light on and off)
  • interpreted by computer
34
Q

Endoscopy- optical fibres

A
  • doctors use so can diagnose or surgery
  • light shone one end- tir
  • light reflects back into another fibre- taking info up to camera so doctor can see
35
Q

Dispertion

A
  • seperating of diff wavelengths (colours) of white light upon reraction through a glass prism
  • roygbiv from top (red at top, violet at bottom)
36
Q

Greater wavelength

A
  • slower the speed

- greater refractive index

Physics (8 decks)

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