STP Physical Sciences 5

Question 1

What is the primary mechanism by which ultrasound causes tissue heating in therapeutic applications?

Accepted Answer

Absorption of acoustic energy converted to heat

Answer

Therapeutic ultrasound heats tissue primarily through absorption of acoustic energy, which is converted to thermal energy as the wave attenuates.

Question 2

Which of the following correctly describes the relationship between photon energy and wavelength?

Accepted Answer

E = hc/λ

Answer

Photon energy E = hf = hc/λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength.

Question 3

What does a quality factor (radiation weighting factor) account for in dose calculations?

Accepted Answer

The biological effectiveness of different radiation types relative to X-rays

Answer

The radiation weighting factor (w_R) accounts for the relative biological effectiveness of different radiation types, converting absorbed dose (Gy) to equivalent dose (Sv).

Question 4

In flow measurement using the Doppler effect in ultrasound, what does the Doppler shift frequency depend on?

Accepted Answer

The velocity of blood, ultrasound frequency, and angle between beam and flow

Answer

The Doppler shift Δf = 2fv·cosθ/c, so it depends on the transmitted frequency, blood velocity, speed of sound in tissue, and the angle between the beam and flow direction.

Question 5

What does the term 'signal-to-noise ratio' (SNR) quantify in a measurement system?

Accepted Answer

The ratio of desired signal power to background noise power

Answer

SNR is the ratio of the power of the desired signal to the power of background noise, with a higher SNR indicating cleaner, more reliable measurements.

(STP) Scientist Training Programme Practice Test

(STP) Scientist Training Programme Practice Test

STP Physical Sciences 5