Part of the beam pattern from any transducer.

• A. Side lobes
• B. Main lobe
• C. Grating lobes
• D. Nulls

Answer: (A)

Side lobes are a constant feature of any transducer's beam pattern. When a finite aperture emits energy, diffraction spreads some energy into directions away from the main beam, producing secondary peaks around the central lobe. These side lobes are inherent to the pattern and reflect energy radiated off-axis, typically at a lower level than the main lobe. Their presence is a fundamental consequence of the finite size and feeding of the aperture, and while techniques like tapering can reduce them, they cannot be completely eliminated. Grating lobes arise only in certain array spacings, nulls are specific angles where the response drops to zero due to interference, and the main lobe is the central, strongest direction of radiation. Among these, side lobes are the part of the pattern you’ll always see in a transducer’s beam.