Which of the following statements is not true? A. Dust in dark clouds scatters v

Question

Which of the following statements is not true?

A. Dust in dark clouds scatters visible light, making them opaque at visible wavelengths.

B. Since dust does not scatter light at sufficiently longer infrared wavelengths, dark clouds are transparent at these wavelengths.

C. Atomic hydrogen and a variety of molecules in dark clouds emit radio light, making them bright at radio wavelengths.

D. Dark clouds that are not collapsing are supported against collapse by a combination of thermal pressure, rotation, and magnetic fields.

E. Dark clouds that are collapsing ultimately form a single system, most likely either a single star or a binary star system.

Explanation / Answer

The statement B is not true.

Infrared wavelength ranges from 0.75 to 300 micrometers. The near-infrared wavelengths, which are just outside the visible spectrum can be used to detect stars, galaxies, and quasars.

Interstellar clouds like a dark nebula or absorption nebula cause the 'extinction'- absorption and scattering of light by interstellar dust, thereby obscuring objects behind them. These larger molecular clouds can only be determined using radio waves or infrared. They do not appear transparent but become visible.

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