Which of the following is the combination that is used in the formation of achromatic lenses? 1 point
1 convex and 1 plane mirror
2 convex lenses
1 convex and 1 concave lens
2 concave lenses

The electric field between square plates of a parallel-plate capacitor has magnitude e. the potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. the magnitude of the electric field between the plates is now equal to a)e b)e/4 c)e/2 d)4e e)2e