In the figure, four long straight wires are perpendicular to the page, and their cross sections form a square of edge length a = 10.0 cm. Each wire carries 8.50 A, and the currents are out of the page in wires 1 and 4 and into the page in wires 2 and 3. In unit-vector notation, what is the net magnetic force per meter of wire length on wire 4? Number n n i+ n '}Units v In the figure, an electron with an initial kinetic energy of 3.80 keV enters region 1 at time t = 0. That region contains a uniform magnetic field directed into the page, with magnitude 0.00540 T. The electron goes through a half-circle and then exits region 1, headed toward region 2 across a gap of 30.0 cm. There is an electric potential difference AV = 1900V across the gap, with a polarity such that the electron's speed increases uniformly as it traverses the gap. Region 2 contains a uniform magnetic field directed out of the page, with magnitude 0.018%9 T. The electron goes through a half-circle and then leaves region 2. At what time t does it leave? Sound waves with frequency 3100 Hz and speed 343 m/s diffract through the rectangular opening of a speaker cabinet and into a large auditorium of length 100 m. The opening, which has a horizontal width of 32.7 cm, faces a wall 100 m away (the figure below). Speaker cabinet Central Along that wall, how far from the central axis of that wall in meters will a listener be at the first diffraction minimum and thus have difficulty hearing the sound? (Neglect reflections.) e (1 O o Entoptic halos. If someone looks at a bright outdoor lamp in otherwise dark surroundings, the lamp appears to be surrounded by bright and dark rings (hence halos) that are actually a circular diffraction pattern as in the figure, with the central maximum overlapping the direct light from the lamp. The diffraction is produced by structures within the cornea or lens of the eye (hence entoptic). If the lamp is monochromatic at wavelength 572 nm and the first dark ring subtends angular diameter 3.2 in the observer's view, what is the (linear) diameter of the structure producing the diffraction? Number n Units nm v