A). 600,000 Hz or 600 KHz
Yes. Commercial broadcasters operate here.
This is the '600' on your AM radio dial.
B). 60 Hz
No. In principle, this frequency might be used for communication or
commercial broadcasting, but it suffers from two inconvenient truths:
-- An efficient antenna for 60 Hz ... either transmitting or receiving ...
needs to be almost 780 miles long.
-- This is the frequency of the electric power utility in the US and
Canada, so every outlet, wire, cable, lamp cord, and electric line
on a pole RADIATES a little bit of signal at this frequency. That's
an awful lot of interference.
C). 6,000,000 Hz or 6 MHz
There's a lot of broadcasting activity here, but it's not commercial
music, news, and sports into local homes and cars.
It's foreign short-wave broadcast, bringing news, propaganda, and
culture from one country to another. Pretty interesting to browse.
D). 6,000 Hz or 6 KHz.
No. Not used for communication, for an interesting reason:
This frequency is smack in the middle of the human hearing range.
So if it were used for communication ... with high-power transmitters
here and there ... then you wouldn't hear it in the air. But wherever
wires were being used to carry sound ... your stereo's speaker wires,
wires from your player to your ear-buds, wires to the telephones in
your house etc ... the wires would act as antennas, picking up
broadcasts at 6 KHz, and the broadcasts would get into everything.
Not a smart plan.
Answer:
Explanation:
——»To measure centimeters, we can use ruler.
- Use a ruler with the side marked either cm or mm. Align the edge of the object with the first centimeter line on the ruler, then find the length in whole centimeters, or the larger numbers on the ruler.
Remember Dark Energy is repulsive, the more the faster the universe expands (indeed accelerates), so the faster it would cool down and increase its size, not the other way. Now, no one knows what it is. For instance, if Dark Energy would rather be some other geometric effect, it could have a different ending than just if it is a cosmological constant term. So far, though, all experimental data do not favor anything else that is not compatible with just a cosmological constant ... We'll need to wait few years (~10 years) to get to know much better this with missions and ground experiments that are undergoing or planned to be launched.
Answer:
True
Explanation:
In 2019 was taken the first image of a supermassive black hole in the center of the galaxy M87 with the Event Horizon Telescope, which is a network of radio telescope located in different points of the Earth, with the purpose of making a telescope of the size of the Earth.
A radio telescope is an antenna that is capable to perceive the light in the radio part of the electromagnetic spectrum¹.
It is important to notice that in the picture what it can be seen is the effect that the black hole has in the nearby stars.
Key terms:
¹Electromagnetic spectrum: decomposition of light in its different wavelengths (from radio waves to gamma rays).
The net force will point towards the acceleration of the object, as supported by Newton's second law.
