Two radio antennas A and B radiate in phase. Antenna B is 120 m to the right of antenna A. Consider point Q along the extension of the line connecting the antennas, a horizontal distance of 40 m to the right of antenna B. The frequency, and hence the wavelength, of the emitted waves can be varied. (a) What is the longest wavelength for which there will be destructive interference at point Q?
(b) What is the longest wavelength for which there will be constructive interference at point Q?

The space within which a test north pole experiences a force magnetic poles 2. a powerful stream of electrons flowing high above the earth in the ionosphere electrojet 3. a concept to explain the directional nature of a magnetic field field lines 4. coil of wire designed to produce a magnetic field by a current passing through its windings ionosphere 5. that region above the earth's atmosphere where particles exist in an ionized state magnetic field 6. the extremities of a magnet where the field lines tend to converge or concentrate aurora borealis 7. a phenomenon that occurs in the northern latitudes; the northern lights solenoid