Final answer:
The relationship between sample volume size and Doppler spectrum can affect the range of velocities detected within a sample, as the Doppler spectrum is broadened with a larger sample volume. This aspect of the Doppler effect is crucial in both medical diagnostics and astronomy for measuring blood flow velocities or the motion and size of stars.
Step-by-step explanation:
The relationship between sample volume size and Doppler spectrum is an aspect of the Doppler effect, observed when there is relative motion between an observer and a wave source. The Doppler effect causes a shift in frequency for waves, such as sound or light, when there is motion towards or away from the observer. In the context of ultrasound used in medical diagnostics, a larger sample volume may gather Doppler data from a wider range of blood cells, which could lead to a broader Doppler spectrum, indicating different velocities within the blood flow. When considering distant stars, the Doppler shift of the spectral lines allows scientists to determine the relative motion of stars. Specifically, absorption lines in the spectrum will shift towards the blue end if the star is approaching or towards the red end if it is receding. This principle also provides a method to measure stellar diameters, as the speed of the moving star can be deduced from the Doppler shift and, with known time intervals, the diameters can be calculated.