Out of the choices given, when a light wave moves from a medium where particles of matter are closely packed to a medium made of little matter. You expect the light wave to move faster and increase its speed.
The percent difference between two numbers
and
is given by

The absolute value is there because we only care about the absolute percent difference, and not taking into account whether we go from
to
or vice versa. If we remove them, we have two possible interpretations of percent difference.
For example, the (absolute) percent difference between 3 and 6 is

In other words, we add 100% of 3 to 3 to end up with 6. This is the same as the percent difference going from 3 to 6. On the other hand, the percent difference going from 6 to 3 is

which is to say, we take away 50% of 6 away from 6 to end up with 3.
"Make comparisons to object measurements" tells us that the differences should be computed relative to "measurements for object". In other words, take
from the left column and
from the right column.



Density =mass/volume
volume=mass/density
volume=1.51g/ 3.52g/ml
volume=4.29ml
Answer:
a. Electric field lines can never cross each other.
d. Wider spacing between electric field lines indicates a lower magnitude of electric field.
Explanation:
a. The electric field lines cannot be crossed, since this would mean that there would be more than one electric field vector for the same point at the place where the crossing occurs.
d. The space between the field lines is inversely proportional to the intensity of the electric field.