20. The half-life of Calcium-47 is 3.91 x 10⁵ seconds. A sample contains 4.11 x 10¹⁶ nuclei. How much of the sample is left after 7.82 x 10⁵ seconds?

1.03 x 10¹⁶ nuclei

5.14 x 10¹⁵ nuclei

2.57 x 10¹⁵ nuclei

2.06 x 10¹⁶ nuclei

24. Which of the following was Einstein's Second Postulate to the Special Theory of Relativity?

A beam of light that traveled parallel to the aether would take longer than the beam that traveled perpendicularly to the aether.

The laws of physics are the same in all frames of reference that are moving uniformly.

The speed of light is constant and is independent of the motion of the source or the observer.

Waves had to have some medium to travel through.

25. Explain how the atomic model went from the billiard ball model to the plum pudding model?

26. What is the rest energy of a neutron? (c = 2.9979 x 10⁹ m/s, m_n = 1.6749 x 10^-27)

8.18 x 10^-14 J

2.73 x 10^-22 J

1.5032 x 10^-10 J

1.5053 x 10^-10 J

28. Describe atomic spectra using the terms of electron shells, emission, absorption, and wavelengths.

29. Which of the following can be used to describe nuclear fission? Check all that apply.

energy is released as light

used in atomic bombs

not very efficient

used in nuclear reactors

30. Which of the following are true regarding beta minus decay? (Select all that apply)

emits an antineutrino

the nucleus emits a high-energy electron

emits a neutrino

the nucleus emits a high-energy positron