Elements above uranium in the periodic table do not exist in any ...

[karlynnae]

Elements above uranium in the periodic table do not exist in any appreciable amounts in nature because they have short half-lives.
 
  Yet there are several elements below uranium in atomic number with equally short half-lives that do exist in appreciable amounts in nature. How can you account for this?
  A) These are isotopes formed by living bodies.
  B) These isotopes were placed in nature by the testing of nuclear bombs.
  C) These isotopes were formed from the fusion of even smaller isotopes.
  D) These isotopes result from the radioactive decay of uranium.

Question 2

When a beam of light that is traveling in glass strikes an air boundary at the surface of the glass, there is
 
  A) a 90 phase change in the reflected beam.
  B) no phase change in the reflected beam.
  C) a 180 phase change in the reflected beam.
  D) a 60 phase change in the reflected beam.
  E) a 45 phase change in the reflected beam.

[jamesnevil303]

Answer to Question 1

Answer: D

Answer to Question 2

B

[karlynnae]

Gracias!

[Mochi]

TYSM