'Red shift' is a key concept for astronomers. The term can be understood literally - the wavelength of the light is stretched, so the light is seen as 'shifted' towards the red part of the spectrum.
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The third choice im pretty sure
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Photosphere - The photosphere is the deepest layer of the Sun<span> that we </span>can<span> .... </span>sun's temperature changes<span> throughout the layers of its </span>atmosphere<span>, we </span>can<span> then order .... generated in the </span>sun's interior<span>affect its lower </span>atmosphere<span>, or chromosphere, .... of the two wave motions, showed a time delay, known as a phase </span>difference<span>.</span>