Hi Shan. Try to view it in this manner. For this will we use a train. As the train approaches, the sound waves from its whistle are compressed towards the observer. The intervals between waves diminish, which translates into an increase in frequency or pitch. As the train recedes, the sound waves are stretched relative to the observer, causing the whistle’s pitch to decrease. By the change in pitch of the whistle, you can determine if the train is coming nearer or speeding away. If you could measure the rate of change of pitch, you could also estimate the train’s speed.

By analogy, the electromagnetic radiation emitted by a moving object also exhibits the Doppler effect. The radiation emitted by an object moving toward an observer is squeezed; its frequency appears to increase and is therefore said to be blueshifted. In contrast, the radiation emitted by an object moving away is stretched or redshifted. As in the train analogy, blueshifts and redshifts exhibited by stars, galaxies and gas clouds also indicate their motions with respect to the observer.

In astronomy, the Doppler effect was originally studied in the visible part of the electromagnetic spectrum. Today, the Doppler shift, as it is also known, applies to electromagnetic waves in all portions of the spectrum. Also, because of the inverse relationship between frequency and wavelength, we can describe the Doppler shift in terms of wavelength. Radiation is redshifted when its wavelength increases, and is blueshifted when its wavelength decreases.

Astronomers use Doppler shifts to calculate precisely how fast stars and other astronomical objects move toward or away from Earth. For example the spectral lines emitted by hydrogen gas in distant galaxies is often observed to be considerably redshifted.

Sunlight on the other hand doesn’t enter into the earth. If this were happening we wouldn’t need lights when we were underground. X-rays on the other hand do, but I don’t know as to what the depth might be, but does depend on the density of a given material.

In astronomy, the Doppler effect was originally studied in the visible part of the electromagnetic spectrum. Today, the Doppler shift, as it is also known, applies to electromagnetic waves in all portions of the spectrum. Also, because of the inverse relationship between frequency and wavelength, we can describe the Doppler shift in terms of wavelength. Radiation is redshifted when its wavelength increases, and is blueshifted when its wavelength decreases.

Astronomers use Doppler shifts to calculate precisely how fast stars and other astronomical objects move toward or away from Earth. For example the spectral lines emitted by hydrogen gas in distant galaxies is often observed to be considerably redshifted.

Dark colored objects will absorb light from the sun where as light colored objects will reflect it. X-rays on the other hand will penetrate 2 feet of soil estimated, but will not penetrate 2 feet of lead. In this case it is the density of the material and not the color. As to how much of an affect X-rays have on the earth I don’t really know, but I do know it does have an affect on the earths magnetic field, which could in turn affect the earth. Take Care…Don in creepy town