-- Looking at the dots casually, they look green because they absorb all other
colors of light, and only green light is left to proceed to your eyes. (In order for
this to work, there has to be some green in the light shining on the dots.
Daylight and most light bulbs work fine.)
-- The filter looks red because it absorbs all other colors of light, and only
the red light is left to pass through the filter and come out on the other side.
-- When the green light from the dots hits the red filter, it's absorbed in the
filter, and there's no light left to come out on the other side.
If you're looking through the filter at the dots, they look <em>black</em>.
There are some more like Time - second (s)
Amount of substance - mole (mole)
Electric current - ampere (A)
Temperature - kelvin (K)
Luminous intensity - candela (cd)
Step-#1:
Ignore the wire on the right.
Find the strength and direction of the magnetic field at P,
caused by the wire on the left, 0.04m away, carrying 5.0A
of current upward.
Write it down.
Step #2:
Now, ignore the wire on the left.
Find the strength and direction of the magnetic field at P,
caused by the wire on the right, 0.04m away, carrying 8.0A
of current downward.
Write it down.
Step #3:
Take the two sets of magnitude and direction that you wrote down
and ADD them.
The total magnetic field at P is the SUM of (the field due to the left wire)
PLUS (the field due to the right wire).
So just calculate them separately, then addum up.
