The schlieren photographic technique is often used to visualize shock waves and other strong but invisible flows. But a sensitive set-up can show much weaker changes in density and pressure. Here, schlieren is used to show the standing sound wave used in ultrasonic levitation. By placing the glass plate at precisely the right distance relative to a speaker, you can reflect the sound wave back on itself in a standing wave, seen here as light and dark bands. The light bands mark the high-pressure nodes, where the pressure generated by the sound waves is large enough to counteract the force of gravity on small styrofoam balls. This allows them to levitate but only in the thin bands seen in the schlieren. Move the plate and the standing wave will be disrupted, causing the bands to fade out and the balls to fall. (Video and image credit: Harvard Natural Sciences Lecture Demonstrations)
Life is full of emotional highs and lows, ranging from enjoying an activity with a loved one and savoring a delicious meal to feeling hurt by a negative interaction with a co-worker or that recent scuffle with a family member. But when we let emotions from one event carry on to the next, such spillover can color our impressions and behavior in those new situations – sometimes for the worse.
The research is in Psychological Science. (full access paywall)
