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Physics > Waves and the Electromagnetic Spectrum > Flashcards

Waves and the Electromagnetic Spectrum Flashcards

1
Q

describe longitudinal waves in terms of oscillation

A

oscillations parallel to the direction of travel

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2
Q

describe transverse waves in terms of their oscillation

A

perpendicular to the direction of wave travel

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3
Q

give 3 examples of longitudinal waves

A
  • sound waves
  • ultrasound waves
  • seismic P-waves
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4
Q

give 5 examples of transverse waves

A
  • ripples on the surface of water
  • vibrations in a guitar string
  • a Mexican wave in a sports stadium
  • electromagnetic waves - eg light waves, microwaves, radio waves
  • seismic S-waves
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5
Q

define amplitude

A

the maximum displacement of a point of a wave from its rest position

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6
Q

define wavelength

A

distance covered by a full cycle of the wave, usually measured from peak to peak, or trough to trough

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7
Q

define frequency

A

the number of waves passing a point each second

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8
Q

define time period (in waves)

A

the time taken for a full cycle of the wave, usually measured from peak to peak, or trough to trough

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9
Q

define wave speed

A

the distance the wave travels in a given amount of time

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10
Q

describe a method for measuring the speed of sound waves in air

A

A person fires a starting pistol and raises their hand in the air at the same time. A distant observer stood 400 metres (m) away records the time between seeing the action (the light reaches the time keeper immediately) and hearing the sound (which takes more time to cover the same distance).

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11
Q

how is frequency related to sound

A
  • high frequency sound waves are high pitched
  • low frequency sound waves are low pitched
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12
Q

how is amplitude related to sound

A

*high amplitude sound waves are loud
*low amplitude sound waves are quiet

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13
Q

what is an electromagnetic wave?

A

A transverse wave caused by oscillations in an electromagnetic field

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14
Q

how is the electromagnetic spectrum grouped?

A

a spectrum containing seven groups going from very long wavelength, low frequency and low energy to very short wavelength, high frequency and high energy

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15
Q

list the groups of electromagnetic waves in order of decreasing wavelength and increasing frequency/ energy

A
  1. radio waves
  2. microwaves
  3. infrared
  4. visible light
  5. ultraviolet
  6. x-rays
  7. gamma rays
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16
Q

why can our eyes only detect visible light?

A

because our eyes can only detect a limited range of electromagnetic waves and visible light contains all the frequencies that can be detected by the human eye.

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17
Q

what colour has the lowest frequencies of visible light?

A

red

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18
Q

what colour has the highest frequencies of visible light?

A

violet

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19
Q

what is refraction?

A

a process by which a wave changes speed and sometimes direction upon entering a denser or less dense medium, eg a light ray changes direction when refracted by a lens
* change in material
* causes change in direction
* causes change in speed

20
Q

how are radio waves produced?

A

by oscillations in electrical circuits

21
Q

what can radio waves be absorbed by?

A

electrical circuits

22
Q

what do changes in atoms and the nuclei of atoms result in?

A

electromagnetic waves being generated or absorbed (over a wide frequency range)

23
Q

what is the angle of refraction less than?

A

the angle of incidence

24
Q

what is the angle of incidence?

A

the angle between the normal line and incident ray

25
Q

what is the angle of refraction?

A

the angle between the normal line and the refracted ray

26
Q

what is the incident ray?

A

the light ray going into/ pointed at an object

27
Q

hazard of radio waves

A

very small rise in temperature

28
Q

hazard of microwaves

A

can cause internal heating of body tissues

29
Q

hazard of infrared

A

radiation is felt as heat and causes skin to burn

30
Q

hazard of visible light

A

from a laser which is very intense can damage the retina at the back of the eye

31
Q

hazard of ultraviolet

A

can damage skin cells and lead to skin cancer and damage the eyes, it can cause skin to age prematurely

32
Q

hazard of x-rays

A

damage cells inside the body causing dangerous ionisation in living cells which damages DNA which can lead to cancer

33
Q

hazard of gamma rays

A

damage cells inside the body causing dangerous ionisation in living cells which damages DNA. This can lead to cell death and cancer.

34
Q

use of radio waves

A

communication

35
Q

why are radio waves used for communication?

A

because they are transmitted easily through air, don’t cause damage if absorbed by the human body, and can be reflected to change direction.

36
Q

uses of microwaves

A

cooking food and for satellite communication

37
Q

why are microwaves used for cooking food and for satellite communication?

A
  • they’re high frequency so easily absorbed in food, increasing the internal energy of the food molecules
  • they pass easily through the atmosphere, so they can pass between stations on Earth and satellites in orbit
38
Q

uses of infrared

A

electrical heaters, cookers, infrared cameras which detect people in the dark

39
Q

why is infrared used for electrical heaters, cookers, infrared cameras which detect people in the dark?

A
  • it has frequencies which are absorbed by some chemical bonds, the internal energy of the bonds increases when they absorb infrared light
  • all objects emit infrared light but the human eye cannot see this light but infrared cameras can detect it so ‘thermal imaging’ is useful for detecting people in the dark
40
Q

uses of visible light

A

fibre optic communications

41
Q

why is visible light used for fibre optic communications?

A

because our eyes can detect it’s wavelengths

42
Q

uses of ultraviolet

A

energy-efficient lamps

43
Q

why is ultraviolet used for energy-efficient lamps?

A

fluorescent substances in the lamps absorb ultraviolet light produced inside the lamp, and re-emit the energy as visible light

44
Q

uses of x-rays and gamma rays

A

internal imaging

45
Q

why are x-rays and gamma rays used for internal imaging?

A

because they are transmitted through body tissues with very little absorption and X-rays are absorbed by dense structures like bones, which is why X-ray photos are used to help identify broken bones

46
Q

how do wave front diagrams work?

A
  • as a wave travels into a denser medium, such as water, it slows down and the wavelength decreases.
  • Although the wave slows down, its frequency remains the same, due to the fact that its wavelength is shorter.
  • if for example the right hand side of the incoming wave slows down before the left hand side does. This causes the wave to change direction.

Physics (27 decks)

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