Recent content by 21joanna12

I have been thinking about coils of wire carrying alternatingcurrent. From what I understand, a back emf is induced in the coil because there is a changing magnetic field around each individual loop of wire, and therefore there is a changing flux through each loop because the changing field...

Thank you for all of the brilliant replies, although I still can't quite wrap my head around this statement. The redshift tells us the recession velocity of the Galaxy, so a galaxy with a certain redshift would have the same recession velocity in an accelerating or not accelerating universe...

i have heard it said that back force occurs in generators and back emf occurs in motors, however I was considering a motor and I thought that it seems to me that as the coil is rotating and it has the changing flux linkage, and thus a back end is induced in it by Lenz's law, this reduces the...

From what I understand, in the equation P=\sigma AT^4, P is the power output of the star which is the energy radiated per second in EM radiation of all frequencies, and I think luminosity is also defined as the energy radiated per second in EM radiation of all frequencies. Therefore luminosity...

Thank you for your reply! It is really how the curve of velocity against distance deviates that I am wondering about. Does it curve upwards? This would suggest that the redshift, and thus recession velocity, is greater than expected for its distance, and therefore the galaxy appears brighter...

I am trying to wrap my brain around the evidence for accelerating expansion of the universe from type 1a supernovae. From what I understand, it was first realized that the universe was expanding at an increasing rate from discrepancies between the calculated distances to type 1a supernovae using...

Thank you all! This has been a very interesting thread! :)

Wikipedia only talks about helium and carbon-oxygen white dwarfs... I understand that on a red giant you only get fusion up to oxygen, but I though that maybe if you had a red supergiant which produced iron in its core, and when it exploded as a supernova it threw off enough mass to form a white...

These two types of stars clearly must have different properties because they form distinct groups on a Hertzsprung-Russell diagram. I have also read that red supergiants can form elements up to around carbon by nuclear fusion, whereas red supergiants can form up to iron, however there doesn't...

I have been looking at these diagrams: From the following link http://www.astronomynotes.com/telescop/s3.htm And I just can't seem to figure out why the first telescope design doesn't show a shadow and in the second why the presence of the secondary mirror, and the hole, do not affect the...

Sorry to tag another question onto this thread, but I was reading a wikipedia article and it said that " Whilst the photosphere has an absorption line spectrum, the chromosphere's spectrum is dominated by emission lines. In particular, one of its strongest lines is the Hα at a wavelength of...

I can't seem to find an answer to this quick question: which part of the star causes the observed spectral lines? As I understand, the photosphere is the deepest visible layer of the star, and then light passes through the chromosphere and the corona. I would think that both the chromosphere and...

I am slightly confused about what the term 'astronomical telescope' covers. My textbook seems to be implying that astronomical telescopes are refracting telescopes with an objective and eyepiece lens, and reflecting telescopes are separate to astronomical telescopes. On the other hand I have...

Thank you for your reply! But I was just wondering why greater angular magnification means smaller field of view- wouldn't you be able to see a larger image with the same field of view if the telescope objectives are the same diameter?

I don't quite understand the concept of field of view of a telescope... Specifically, I am trying to understand the advantages of reflecting and refracting telescopes compared with the other, and my textbook says that "Refracting telescopes have a wider field of view than reflectors of the same...