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Medical Physics > Lecture 2 > Flashcards

Lecture 2 Flashcards

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1
Q

What is the definition of oscillations

A

Movements or processes that, to one degree or another, repeat over time

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2
Q

When are oscillations periodic

A

if: x(t) = x(t+nT)

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3
Q

How is energy transferred in wave motion

A

Over a distance

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4
Q

The two main types of waves

A

Mechanical waves
Electromagnetic waves

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5
Q

Mechanical waves

A

-Some physical medium is being distributed
-The wave is the propagation of a disturbance through a medium

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6
Q

Electromagnetic waves

A

-No medium required
-For example; light, radio waves and x-rays

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7
Q

What is a wave/process?

A

The process of propagation of oscillations in a continuous medium

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8
Q

One fundamental property of all waves

A

The transfer of energy without the transfer of matter

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9
Q

What is the crest

A

The location of the maximum displacement of the element from its normal position

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10
Q

What is the amplitude (A)

A

The distance between the resting position and maximum displacement

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11
Q

What is the wavelength

A

The distance from one crest to the next crest

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12
Q

What is the period (T)

A

The time interval required for two identical points of adjacent waves to pass by a point

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13
Q

What is the frequency (v)

A

The number of crests (or any point on the wave) that pass a given point in a unit time interval

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14
Q

Longitudinal waves

A

Mechanical waves in which the oscillations of the particles are in the direction of propagation of the wave

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15
Q

Transverse waves

A

Waves in which the oscillations are in a direction perpendicular to the direction of propagation of the wave

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16
Q

Which types of waves can propagate in liquids and solids

A

-Both longitudinal and transverse waves can propagate in a solid
-Only longitudinal waves can propagate in liquids

17
Q

Compression and rarefaction definitions

A

-An increase in pressure is compression
-Decrease in pressure is rarefaction

18
Q

What is sound

A

An elastic wave with a frequency in the range of 16-20,000Hz.

This is the hearing diapason of the human ear

19
Q

3 types of sound waves

A

-Audible waves
-Infrasonic waves
-Ultrasonic waves

20
Q

Audible waves

A

They are within the sensitivity of the human ear (20Hz-20kHz)

21
Q

Infrasonic waves

A

Have the frequencies below the audible range (less the 20kHz)

22
Q

Ultrasonic waves

A

Have frequencies above the audible range (larger than 20kHz)

23
Q

What type of wave is the speed of sound greater in solids

A

-Longitudinal waves
-The speed of sound in highly elastic solids, such as steel, reaches 5000-6000m.s^-1

24
Q

What is impedance

A

Media are characterised by a certain acoustic resistance

25
Q

How can the reflection and transmission coefficients of the sound wave be calculated

A

By knowing the acoustic impedances of two materials

26
Q

What does a greater difference between the acoustic impedances lead to

A

The greater part of the incident sound wave is reflected back into the medium

27
Q

What is the Doppler Effect

A

The apparent change in frequency (or wavelength) that occurs because of the motion of the source or observer of a wave

28
Q

Features of the Doppler Effect

A

-When the relative speed of the source and the observer is higher than the speed of the wave, the frequency appears to increase

-When the relative speed of the source and observer is lower than the speed of the wave, the frequency appears to decrease

29
Q

Sound pressure (p)

A

The additional periodically changing component of the pressure in the medium is caused by sound propagation.

Sound pressure is measured in Pascals (Pa)

30
Q

Wave intensity

A

For waves, the intensity value represents the energy carried by the wave per unit of time through a perpendicular unit area

31
Q

What is the threshold of hearing

A

This is the sound pressure level (SPL) of 20 micro pascals

32
Q

What is the absolute threshold of hearing (ATH)

A

-The minimum amplitude of a pure tone that the average ear with normal hearing can hear in a noiseless environment

-The ATH curve rises with age, as the human ear becomes more insensitive to sound

33
Q

What is the threshold of pain

A

-The SPL beyond which sound becomes unbearable for a human listener
-Prolonged exposure to sound pressure levels over the threshold of pain can cause physical damage, potentially leading to hearing impairment

34
Q

What is a pure (simple) tone

A

A sound with a certain frequency, e.g a tuning fork

35
Q

What is a complex tone

A

It is made up of multiple simple tones

36
Q

What is the acoustic spectrum

A

The totality of the fundamental tone and overtones represented by their relative amplitude (relative to the amplitude of the fundamental tone)

37
Q
A

Medical Physics (3 decks)

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