Parallel laser beam (=550 nm) falls perpendicularly on the opaque screen that has a circular opening with diameter D=2 mm. A dark spot is observed at a distance b1=18 cm on the central axis behind the screen. What is the minimal distance b that one has to move away from this spot and further away from the screen in order to observe a dark spot again?

probably not the "magnets"in the magnet, so to speak, are thought to be electrons orbiting in shells. vurrent loops two sides to the loop

igneous rocks also form where plates converge. the subducting plate melts as it sinks into the crust of the earth, and the melt rises into the overriding plate forming volcanoes. metamorphic rocks are formed mainly in the lithosphere, wherever there is high pressure and high temperature. -woods