Why can we never see the backside of the moon from earth?

Aray of light traveling parallel to the principal axis of a concave mirror will be reflected through the mirror's

Abeam of electrons with of wavelength of 7.5 x 10-6 m is incident on a pair of narrow rectangular slits separated by 0.75 mm. the resulting interference pattern is projected onto a screen 10.0 m from the slits. what is the separation of the interference maxima in the resulting interference pattern?

Within a pendulum, as potential energy decreases, energy increases. a. heat b. kinetic c. frictional d. gravitational