CBET Applied Physical Science for Medical Devices (Fluid Dynamics, Acoustics, Optics)

Question 1

According to Poiseuille's Law, if the radius of an IV catheter is halved, how does the maximum flow rate through it change (assuming all other variables remain constant)?

Accepted Answer

It decreases to one-sixteenth (6.25%)

Answer

It decreases by half (50%)

Answer

It decreases to one-quarter (25%)

Answer

It decreases to one-eighth (12.5%)

Question 2

A pulse oximeter uses two wavelengths of light — typically 660 nm (red) and 940 nm (infrared). Why are these two specific wavelengths chosen?

Accepted Answer

Oxyhemoglobin and deoxyhemoglobin have opposite absorbance ratios at these wavelengths, enabling their proportional calculation

Answer

They penetrate skin to different depths, allowing tissue depth profiling

Answer

660 nm activates the photodetector and 940 nm is the reference channel

Answer

These wavelengths avoid interference from skin melanin, which absorbs all other visible light

Question 3

The Doppler effect in medical ultrasound is used to measure blood flow velocity. If blood is flowing TOWARD the transducer, how does the received frequency compare to the transmitted frequency?

Accepted Answer

The received frequency is higher (positive Doppler shift)

Answer

The received frequency is lower (negative Doppler shift)

Answer

The received frequency is the same (Doppler shift only applies to moving transducers)

Answer

The frequencies alternate between higher and lower with each heartbeat

Question 4

In fiber optic light delivery systems used in surgical endoscopes, what phenomenon allows light to travel through the fiber without escaping through the sides?

Accepted Answer

Total internal reflection at the core-cladding interface when the angle of incidence exceeds the critical angle

Answer

Constructive interference between photons in the fiber core

Answer

The fiber is coated with a reflective metallic layer that bounces light forward

Answer

Polarization of light by the fiber material confines it to the central axis

Question 5

Medical air compressors used in hospitals must supply air at a regulated pressure to power pneumatic devices. According to Boyle's Law, if a compressed air tank at 2000 PSI is connected to a regulator and the output is set to 50 PSI, approximately what fraction of the original gas volume is delivered at the regulated pressure?

Accepted Answer

40 times the original compressed volume

Answer

1/40th of the original compressed volume

Answer

The volume is unchanged — only pressure changes

Answer

4 times the original compressed volume

Question 6

Ultrasound transducers used in diagnostic imaging are based on the piezoelectric effect. What does this effect describe?

Accepted Answer

The conversion between mechanical stress/deformation and electrical charge in certain crystals

Answer

The generation of heat when a material is exposed to high-frequency sound

Answer

The absorption of sound energy by dense biological tissue such as bone

Answer

The refraction of sound waves at tissue boundaries with differing acoustic impedance