# Help i really nead help with me home werk Q ?i have 2 ?

Question:what is the electromagnetic spectrum? and hers my other Q what is the main purposewof a telescole?

This is what the electromagnetic specturm is...

http://imagine.gsfc.nasa.gov/docs/scienc...

This is what the main purpose of a telescope is...

Hope this helps! =)
go to answers.com at search of site type electro magnetic spectrum you get related links , take your pick . Regarding your second question , i think it is telescope what your referring to , assuming that , type telescope at search of answers.com you get hints choose the appropriate one.
1.The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. The "electromagnetic spectrum" (usually just spectrum) of an object is the frequency range of electromagnetic radiation with wavelengths from thousands of kilometres down to fractions of the size of an atom. It is commonly said that EM waves beyond these limits are uncommon, although this is not actually true. The short wavelength limit is likely to be the Planck length, and the long wavelength limit is the size of the universe itself (see physical cosmology), though in principle the spectrum is infinite.

Electromagnetic energy at a particular wavelength λ (in vacuum) has an associated frequency f and photon energy E. Thus, the electromagnetic spectrum may be expressed equally well in terms of any of these three quantities. They are related according to the equations:

wave speed (c) = frequency x wavelength

where:

* c is the speed of light, 299,792,458 m/s (exact)
* h is Planck's constant, (h \approx 6.626069 \cdot 10^{-34} \ \mbox{J} \cdot \mbox{s} \approx 4.13567 \ \mathrm{\mu} \mbox{eV}/\mbox{GHz}).

So, high-frequency electromagnetic waves have a short wavelength and high energy; low-frequency waves have a long wavelength and low energy.

When light waves (and other electromagnetic waves) enter a medium, their wavelength is reduced. Wavelengths of electromagnetic radiation, no matter what medium they are travelling through, are usually quoted in terms of the vacuum wavelength, although this is not always explicitly stated.

2.The main purpose of a telescope is to gather light, i.e. to collect and focus photons. We can think of a telescope then as a "light bucket" - the bigger the bucket, the more photons a telescope can collect.

In addition, a telescope can allow a more detailed view of the structure of a celestial source or to infer that there are two sources, not just one. In an astronomical image, the smallest angular separation between sources (or structures within the image of a single extended source) is called the ANGULAR RESOLUTION. The size of the smallest "point" source in an image is called the image's SEEING.

The minimum angular separation of two sources that can be distinguished by a telescope depends on the wavelength of the light being observed and the diameter of the telescope. This angle is called the DIFFRACTION LIMIT

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