Boys start to get acne at the age of approximately 12 years, with a range of 9 to 15 years old. As most girls will attest, boys on average mature later than girls. Early on in the onset of teen acne, the main lesions are blackheads and whiteheads.
The angular size (angular diameter, apparent size) of an object as seen from a given point is the visual diameter of the object measured as an angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its center that is perpendicular to the viewing direction.
All Answers (16) 1  high frequency = high spatial resolution but limited depth of penetration. low frequency = greater depth of penetration but lower spatial resolution. 2  The spatial resolution of ultrasound is actually quite good. The limitation is that the field-of-view is usually smaller than other imaging techniques. Ultrasound is also constrained by not being able to image through bone or gasses. ... Â·. higher frequency = higher spatial resolution but less depth of penetration.