Answer:
4.30 x 10⁵ N/C
Explanation:
Two positive +3.0-μC point charges at opposite corners of the square creates equal and opposite electric field at the center. hence the electric field by these two positive charges at opposite corners becomes zero.
= length of the square of side = 0.50 m
= distance of the center from each corner = 
Magnitude of net electric field at the center is given as

The change of color. Each color has a different wavelength therefore a different frequency.
Answer:
the period of the 16 m pendulum is twice the period of the 4 m pendulum
Explanation:
Recall that the period (T) of a pendulum of length (L) is defined as:

where "g" is the local acceleration of gravity.
SInce both pendulums are at the same place, "g" is the same for both, and when we compare the two periods, we get:

therefore the period of the 16 m pendulum is twice the period of the 4 m pendulum.
There is approximately 2.54 cm that equals to 1 inch. So your closet answer would be the first choice. :)