The Sine Wave and Sine Wave Patterns Flashcards
Define sin
Right angle triangle
Sine of angle = opposite side
__________
hypoteneuse
Describe the sin graph
X - axis: different angles of angle A
Y-axis: the length of the opposite side to angle A = d
d = opposite side to angle A r = hypoteneuse adjacent to angle A
d = r Sin A
Morphology –> repeating sin graph
What does 90 degrees ‘out of phase mean’
When two sine graphs are compared the degree to which they differ along the X axis (i.e. Angle A) is the degree to which they are ‘out of phase
What is the wavelength of a sine wave
The wavelength is the distance between any two corresponding points in successive cycles e.g. The distance between two peaks and troughs
WHat is the amplitude of a sine wave
Give practical examples of large and small amplitude waves
The maximum displacement of the wave from the horizontal axis
Sound: LArge amplitude –> loud. Small amplitude = soft
Light: LArge amplitude bright and small amplitude dim
Define frequency
The number of complete cycles which occur in one second
Frequency = cycles/seconds
SI unit: hertz (Hz)
e. g. 10 Hz = 10 cycles per second
- -> the time taken for 1 complete cycle is one tenth of a second
Define the period of a sine wave
The time taken for one complete cycle
The period is the reciprocal of the frequency
T(period) = 1/f
How is the velocity of a wave motion calculated
Velocity = distance/time Velocity = wavelength/period
Therefore,
Velocity = Wavelength x Frequency
What is the velocity of sound
330 m/s
If velocity is fixed then frequency and wavelength are interrelated: the higher the frequency the shorter the wavelength and vice verse
What is pitch?
Sound waves with different frequencies are heard with different pitches
Short frequency means long wavelength and low pitch
High frequency means short wavelength and high pitch
Describe how the concept of pitch can be paralleled whilst describe the frequency of light
A light with high frequency (and short wavelength) BLUE
A light with lower frequency and longer wavelength: RED
Summarize the electromagnetic spectrum including real life examples
EXAMPLE WAVELENGTH
Radio / TV / Radar 10 ( Paging systems)
Microwaves 10^-3 (Definition of a second)
Infrared 10^-6 (Infrared analyzers)
Visible 700 - 380 x 10^-9 (Refracrtometry and oximetry)
Ultra-violet 400 -10 x 10^-9
X-rays 10^-12 (Radiology and radiotherapy)
Gamma rays 10^-15
How is 1 second of time defined
The second is defined in terms of the frequency of radiation emitted by atoms of caesium-133.
What is the doppler effect?
Sound waves are repeating regions of high an low pressure through the medium that they travel (e.g. air). These waves travel at a constant velocity. The velocity of the sound wave is equal to the wavelength x frequency. This means that as velocity is constant frequency is inversely proportional to the wavelength. High frequency sound waves are heard at high pitch. Low frequency sound waves are heard at low pitch. If the source of a sound is not moving, the wavelength and frequency remain unchanged. As the velocity of the sound wave remains constant, if the source of the sound is moving closer and further away from the ear (or receiver) the wavelength and frequency will vary. As the sound source moves closer the frequency will increase –> higher pitch. As the sound moves further way the frequency will decrease. This change in frequency and pitch is known as the doppler effect and has multiple applications in medical devices.
Why does ultrasound gel improve the performance of the ultrasound equipment
When sound waves travel through the boundaries between substances of different densities, some of the sound waves are transmitted through the new density but varying proportions of the sound waves are reflected back to the source and some are scattered. The degree of difference in adjacent substance densities determines the degree of attenuation of ultrasound transmission. Air has a very low density compared to all tissues. This significant density discrepancy leads to pronounced attenuation of the ultrasound waves. Ultrasound gel reduces the difference in densities through which the sound waves travel which greatly improves the performance of the device.
Is the doppler effect used to produce images on the monitor of an ultrasound. Substantiate your answer
No. The doppler effect detects the change in frequency of the moving blood cells relative to the probe and generates an audible sound related to the flow velocity.
Images are formed via a different application of ultrasound technology.
- Ultrasound waves are reflected off boundaries and interfaces between substances of different densities
- The same transducer is used to transmit and receive the ultrasound waves and is NOT the dopplar effect but the time taken for the ultrasound wave to travel from the transducer and return which allows the depth of boundary or change in density to be measured
- This mechanical signal is converted into an electrical one via the transducer (containing the piezoelectric crystal) and displayed as an image on a monitor
The probe contains small individual piezoelectric crystals arranged in a line to display a cross section through the body
What is a clinical use of ultrasound waves that are absorbed by tissues
Physiotherapy: High intensity ultrasound used by physiotherapists to provide local heating
With regard to ultrasound, what is cavitation
If very high power ultrasound is used, the pressure in the sound wave can fall to 0 during the minimum of the waveform and this can result in the rapid creation and collapse of bubbles in tissues, a potentially damaging process known as cavitation.
Define interference
The interaction of two or more sine waves and the resulting wave depends on the phase of the two wave motions which interfere
How does a refractometer measure the concentration of halothane in Oxygen?
- Two light beams pass through the refractometer - one through sample chamber (with halothane) other through reference chamber (without halothane)
- The two beams are combined
- If in phase - bright fringe produced (amplitudes additive) If out of phase - dark fringe produced (amplitudes subtract). An array of light and dark fringes results.
- When halothane is added to the SAMPLE chamber it reduces the velocity of light passing through the SAMPLE chamber and alters the phase relationships when the two light beams are recombined
- So a displacement of fringe pattern occurs which may be observed and measured through an eye-piece.
THE DISPLACEMENT OF A SELECTED FRINGE IS DIRECTLY PROPORTIONAL TO THE CONCENTRATION OF GAS ADDED TO THE SAMPLE CHAMBER
What is the important limitation of a refractometer
Calibration required for specific gases/volatiles
Hence cannot identify component gases in a mixture so these must be known in advance.
What is an interference filter. give an example of a device in which an interference filter is used.
An optical component used to select one wavelength from a spectrum of wavelengths. Filters of this type are useful for selecting the required wavelength of infrared radiation for use in an infrared analyser
What is Fourier analysis? What are the 2 main concepts in Fourier analysis
The mathematical process of analysing complex wave patterns into a series of simpler sine wave patterns. This process helps in understanding the patterns of biological electrical signals
- Complex wave pattern may be analysed into a large number of sine wave components
- Sharp spikes mean high-frequency components and smooth rounded patterns consist of a more limited range of frequencies
