there is no written rule that I am aware of, but common sense would indicate the bottom of the fixture should be at least 18" above the head of a 6ft tall person
There is no specific width for fixtures. It is more of an aesthetic value. If it looks good and ties into your theme then use it.
The width of the aperture through which light is passing should be comparable to the wavelength of that light.
After you measure the width of the door, you can use any unit of length you like to describe it. No unit is 'correct' or incorrect, but there's always one that produces the most convenient number ... the number that's easiest to write down, remember, and tell other people about. For the width of a door, I think inches would be a bit more convenient than feet.
The Milky Way spiral galaxy is about 100,000 light years in diameter, and about 3,000 light years thick at its center, and about 1,000 light years thick near its outer edge.
535meters in width of the new dome.
Thew width of Neptune is exactly 72.9m long
The standard height from the top of your table to the bottom of the light fixture above should be between 30"-36". Also the size of the fixture should be a little bit greater than 50% the width of the table itself.
Volume.
WIDTH="80"
(6*5) * 5 = 150
yes
There is no correct order. Give them in any order and, if relevant, state which one is which.
It's width to length ratio is 3 : 8.
Light-years
10^-4 light years
2,000,000,000 pm
That is correct. Volume is height x length x width.
This phenomenon is called diffraction. when light is incident on the opaque substances having width comparable to wavelength of light then light bend.