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Two radio antennas are 300 m apart on a north-south line. The two antennas radiate in phase at a frequency of 3.1 MHz. All radio measurements are made far from the antennas. The smallest angle (excluding the central maximum), measured north of east from the antennas, at which destructive interference of the two radio waves occurs, is closest to: 183 72 359 621 Question 6 1 pts A metallic sheet has a large number of slits, 2.5 mm wide and 10 cm apart, and is used as a diffraction grating for microwaves. A wide parallel beam of microwaves is incident normally on the sheet. What is the smallest microwave frequency for which only the central maximum occurs? 30 GHZ 3 GHz 30 MHz 3MHZ A single slit forms a diffraction pattern, with the rst minimum at an angle of 25 from central maximum. Monochromatic light of 490 nm wavelength is used. The width of the slit is closest to: 592x106m 274x106m 711x106m llxlUm Question 8 1 pts A 24 mm wide diffraction grating has rulings of 600 lines per mm. Light is incident normally to the grating. The longest wavelength that forms an intensity minimum in the third order is closest to: 692x104m 117x104m 334x104m 843x104m