Consider the portion of the video that starts with the all-sky view of the milky way and then zooms in to the galactic center. all of the images except the first two show radio, infrared, or x-ray light. why don't these images show visible light? a. interstellar dust in the galactic disk prevents us from seeing the galactic center with visible light. b. the galactic center is too far away to be seen by the world's largest visible-light telescopes. c. a few nearby stars happen to be located directly between us and the galactic center, preventing us from seeing into the galactic center. d. objects near the galactic center do not emit any visible ligh

b) phosphorus pentoxide

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i think the answer would be b

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.