The Physics of Waves: Light Waves, Sound Waves and Ultrasound
A typical sound produced by a Doppler device when used to assess the speed of blood flow in the brachial artery is triphasic. That is, there are three sounds. Why is this?
Blood flow through elastic arteries is pulsatile.
The three sounds correspond to the pumping action of the left ventricle, the right ventricle and the left atrium.
Blood flow is affected by the actions of the left ventricle and by lung inhalation and exhalation.
The sounds are the original ultrasound frequency, the changed reflected frequency and the frequency of the beats between the two frequencies.
Blood flow through elastic arteries is pulsatile.
Blood flow is fastest as the left ventricle contracts. The velocity of blood flow decreases between contractions. In fact flow is momentarily retrograde as the aortic valve fills and closes. Then forward flow continues as the elastic artery walls recoil from being distended. The other answers are nonsense.
Blood flow through elastic arteries is pulsatile. Blood flow is fastest as the left ventricle contracts. The velocity of blood flow decreases between contractions. In fact flow is momentarily retrograde as the aortic valve fills and closes. Then forward flow continues as the elastic artery walls recoil from being distended. The other answers are nonsense.
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The term “refraction” may be applied to which of the following?A. The effect on light rays as they enter the cornea of the eye
B. Light rays from an object meeting at a point to form a sharp image
C. A light ray travelling away from a surface at the same angle that the light ray approached the surface
D. A light ray travelling through a glass with a faster speed than it would have in air
The unit called the decibel (dB) is used in the measurement of:
A. Sound frequency (pitch)
B. Sound intensity (energy)
C. Sound pressure
D. Sound level (loudness)
In a wave, what is the distance between two adjacent troughs called?
A. The period
B. The displacement
C. The amplitude
D. The wavelength
What will a sound of frequency 250,000 Hz be?
A. Audible
B. Painful to listen to
C. Ultrasonic
D. Close to the threshold of hearing
Visible light waves are examples of:
A. Electromagnetic waves
B. Mechanical waves
C. Longitudinal waves
D. Compressional waves
Which is the BEST definition of a wave?
A. The method by which the energy carried by visible light is propagated.
B. Travelling oscillations in the magnitude and direction of electric and mag-netic fields that do not require a material medium.
C. A periodic disturbance in some property of the medium, the medium itself remains (relatively) at rest.
D. A mechanism for the transfer of energy without the transfer of matter.
Which of the following sound levels, if prolonged, will damage the hearing mechanism of the ear without being perceived as painful?
A. 50 dB
B. 70 dB
C. 90 dB
D. 120 dB
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