# Science And PhYsics HW HELP!

Hello everyone. I have a question and I'm not sure how to answer it.

Q: Name the types of electromagnetic radiation that are used to obtain images of Earth from space. In each case include a concise description as well as the frequency or wavelength range.

BTW, I think I'll probably be only using this thread each time I need help, so I hope that's okay with everybody!

## Answers and Replies

Related Introductory Physics Homework Help News on Phys.org
HallsofIvy
Science Advisor
Homework Helper
Invisible said:
Hello everyone. I have a question and I'm not sure how to answer it.

Q: Name the types of electromagnetic radiation that are used to obtain images of Earth from space. In each case include a concise description as well as the frequency or wavelength range.

BTW, I think I'll probably be only using this thread each time I need help, so I hope that's okay with everybody!
Well, I suppose one could put a big mirror in orbit, then look at it through a telescope and see an image of the earth in the mirror: that would be using light but i don't believe that's ever actually been done.

The only way I can think of that electromagnetic radiation has been used to get images of the earth from space is by relaying bitmapped pictures by radio waves. Hmmm, do they use micro-waves for that now?

Question: The nearest star, Alpha Centauri A, is 4.07 x 10^16 m from Earth.

a. How many light years is it away from Earth?
b. What is the advantage of stating stellar distance in light years rather than meters?

Part A, I got stuck because I don't know wheither to use the distance from the star to Earth, or the 9.46 x 10^15 m which is the distance light can travel in 1 year.

I'm not sure, but for Part A, I divided the distance from AC to Earth by the distance light travels in one year and got 4.30 light-years. I don't know if I did it right, so can someone check my solution?

And I have no idea what this answer is:

What is the advantage of stating stellar distance in light-years rather than meters?

Last edited:
Invisible said:
Question: The nearest star, Alpha Centauri A, is 4.07 x 10^16 m from Earth.

a. How many light years is it away from Earth?
b. What is the advantage of stating stellar distance in light years rather than meters?

Part A, I got stuck because I don't know wheither to use the distance from the star to Earth, or the 9.46 x 10^15 m which is the distance light can travel in 1 year.

I'm not sure, but for Part A, I divided the distance from AC to Earth by the distance light travels in one year and got 4.30 light-years. I don't know if I did it right, so can someone check my solution?

And I have no idea what this answer is:

What is the advantage of stating stellar distance in light-years rather than meters?

for B i wud assume its because in meters the distances are huge so to use them in light years tends to make it a bit easier to understand ..... (just a guess)

and yes you should divide the distance between AC and Earth by the distance light travels in a year, but 4.3 light years sounds wrong m8 i believe closest star is 20 light years + away ..... not sure tho just my 2 cents

BananaMan said:
for B i wud assume its because in meters the distances are huge so to use them in light years tends to make it a bit easier to understand ..... (just a guess)
That IS the answer. We never want to write really big or small numbers, because it's more work to write and it is more difficult to comprehend. A second reason to use lightyears is because it gives us the amount of time we are looking in history of the specific star.

HallsofIvy
Science Advisor
Homework Helper
And, yes, alpha centuari (strictly speaking proxima centauri is the star closest to earth- alpha centauri is actually a triple star system with "proxima" be the one of the three closest) is about 4.3 light years from earth- certainly not "20 light years"!