Pierce conducts an experiment in which waves collide in a way that the energy increases. What has occurred? refraction reflection constructive interference destructive interference

The place you get your hair cut has two nearly parallel mirrors 6.00 m apart. as you sit in the chair, your head is 2.00 m from the nearer mirror. looking toward this mirror, you first see your face and then, farther away, the back of your head. (the mirrors need to be slightly nonparallel for you to be able to see the back of your head, but you can treat them as parallel in this problem.) how far away does the back of your head appear to be?

Is there a point between a 10 nc charge and a 20 nc charge at which the electric field is zero?

Acamcorder has a power rating of 20 watts. if the output voltage from its battery is 9 volts, what current does it use?