1) Archeologists have found fossil remains of some of the first land animals in layer C. It has been suggested that C-14 be used to data the
fossils. Some archeologists have objected and suggested that it would
be best to use U-238 or Pb-206 to date the rock layer instead. Why
would they make such a suggestion?
A)
Rocks do not contain any elemental carbon for
radiometric dating purposes.
B)
Carbon-14 is only found in living things; it can only
be used to date remains.
C-14 has a very short half-life, 5700 years, and based
C) on geologic history, layer C may be several million
years old.
C-14 has such a long half-Life, 570000 million years,
D) it would be more appropriate to use a radioactive
element with a shorter half-life.

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.

the ima (higher than 1m) will be greater than the ima with the height of 1m.