Answer:
The width of the central bright fringe on the screen is observed to be unchanged is 
Explanation:
To solve the problem it is necessary to apply the concepts related to interference from two sources. Destructive interference produces the dark fringes. Dark fringes in the diffraction pattern of a single slit are found at angles θ for which

Where,
w = width
wavelength
m is an integer, m = 1, 2, 3...
We here know that as
as w are constant, then

We need to find
, then

Replacing with our values:


Therefore the width of the central bright fringe on the screen is observed to be unchanged is 
I believe the answer is D. The milky way is a spiral galaxy, You can tell just by looking at it.
Explanation:
It is based upon the fact that " The light travels faster then sound." As the speed of light is faster then the speed of sound, light travels 300,000 km per second and sound travels 1192 km per hour. That is why we observe the lightening first and hear the the sound of thunder later.
You can do this experiment by yourself. Once you see the lightening start counting the seconds until you hear the sound of thunder.Then divide the seconds by 5, you will find out how many miles away the lightening strike was.
Answer:
Electrons move through the wires in the opposite direction.
Explanation:
The direction of an electric current is by convention the direction in which a positive charge would move. Thus, the current in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery.
Answer:
Are you trying to calculate the net force?
If so, it would be 3 N Up.
This is because the 15 N forces from the left and right cancel out, leaving only the upwards 15 N force, and the 12 N force. However, we have to subtract 12 from 15, leaving the final net force to be 3 N Up.
Let me know if this helps!