All points on a wavefront or at a source are point sources for the production of spherical secondary wavelets. This is described by which principle?

All points on a wavefront or at a source are point sources for the production of spherical secondary wavelets. This is described by which principle?

• A. Huygens principle
• B. Snell's law
• C. Fourier theorem
• D. Doppler effect

Answer: (A)

Huygens' principle states that every point on a wavefront acts as a source of its own spherical secondary wavelets, and the next wavefront is the surface tangent to these wavelets. In ultrasound, each small region of the transducer or each point on a propagating front behaves as a point source radiating spherical waves. The overall beam that moves through tissue is the envelope formed by these secondary wavelets as they interfere and propagate together. This idea explains how wavefronts propagate, bend, and diffract as they travel. Snell's law describes how waves refract at boundaries between media with different speeds, which is about changing direction across interfaces rather than forming the next wavefront from a front. The Fourier theorem deals with decomposing signals into frequency components, not the construction of a propagating wavefront. The Doppler effect concerns shifts in frequency due to motion, not the generation of the wavefront from multiple sources.

Huygens' principle states that every point on a wavefront acts as a source of its own spherical secondary wavelets, and the next wavefront is the surface tangent to these wavelets. In ultrasound, each small region of the transducer or each point on a propagating front behaves as a point source radiating spherical waves. The overall beam that moves through tissue is the envelope formed by these secondary wavelets as they interfere and propagate together. This idea explains how wavefronts propagate, bend, and diffract as they travel.

Snell's law describes how waves refract at boundaries between media with different speeds, which is about changing direction across interfaces rather than forming the next wavefront from a front. The Fourier theorem deals with decomposing signals into frequency components, not the construction of a propagating wavefront. The Doppler effect concerns shifts in frequency due to motion, not the generation of the wavefront from multiple sources.