Modern Physics

Question 1 (8 points)

a. Fill in the blanks in the following paragraph to correctly describe the nucleus of an atom. (2 points)                        and                         are the two types of nucleons that make up a nucleus. The                         force exists between                         in the nucleus because of their charge. Because it is repulsive, this force tends to make a nucleus                         . However, the                         force acts between protons, between neutrons, and between protons and neutrons. This force helps to make a nucleus                         , because it is always attractive.

 

  1. How does the total mass before a nuclear reaction compare with the total mass after a nuclear reaction? How does Einstein’s equation address this difference? (1 point)

 

  1. Complete the table below to review the main types of radiation. (2 points)
Radiation Symbol Mass
number		 Charge       

Penetrating

      

ability
Alpha particle        
Negative beta
particle (electron)		        
Positive beta
particle (positron)		        
Gamma ray        
  1. Write the symbol for the nucleus that completes each nuclear equation. (1 point each)

Question 2 (4 points)

a. What happens to a radioactive isotope over the course of 1 half-life? (1 point)

 

  1. How does the half-life of an isotope relate to the stability of its nucleus? (1 point)
  2. Complete the following table to show how to determine the amounts of parent and daughter nuclei and the time passed with each half-life. (2 points)
Number of
half-lives		 Fraction of
original
isotope
remaining		 Fraction of
original
isotope
changed to
daughter
isotope		 Ratio of
parent
isotope to
daughter
isotope		       

      

Time

      

      
0 1 0 1:0 0
1     20 days
2   1:3  
3        

Question 3 (3 points)

a. Review nuclear fission and nuclear fusion by placing X’s in the appropriate boxes. (2 points)

  Nuclear
fission		 Nuclear
fusion
Converts matter into energy    
Occurs in nuclear power plants    
Splits a nucleus    
Produces radioactive waste    
Uses hydrogen    
Occurs in the Sun    
Uses uranium    
Creates limited fuel    
Creates abundant fuel    
  1. What conditions are required for nuclear fusion that prevent it from being used to generate electric energy? (1 point)

 

Question 4 (4 points)

a. In quantum mechanics, what does wave-particle duality describe? (1 point)

 

  1. What does the term quantized light mean? (1 point)

 

  1. Fill in the blanks in the following paragraph to correctly identify phenomena that help provide evidence for the particle nature of light. (2 points)

    A(n) _______________ absorbs energy and then emits electromagnetic radiation based on its _______________. Classical physics predicted that at a high enough temperature, _______________ light would be emitted. Instead, white light was emitted, resulting in the ultraviolet _______________. The photoelectric effect occurs when light shining on a metal creates a(n) _______________. However, only light of a certain minimum _______________ causes electrons to flow. Gas atoms excited by an electric current emit bands of colors of light in a(n) _______________. Each narrow band of light is associated with _______________ of a specific energy.

Question 5 (3 points)

a. In what frames of reference does special relativity apply? (1 point)

 

  1. In what frames of reference must general relativity be used? (1 point)

 

  1. Describe what happens to time and length at speeds close to the speed of light. (1 point)

 

Question 6 (3 points)

a. Describe the big bang theory. (1 point)

 

  1. Match each model of the universe with the future it predicts. (1 point)

    A. Closed
    B. Flat
    C. Open

    _____ The universe will stop expanding but will not collapse.

    _____ The universe will continue to expand forever.

    _____ The universe will stop expanding and then collapse back to its point of origin.

c. Match each observation to the conclusion it supports in the big bang theory. (1 point)

A. Light from other galaxies is shifted toward the red end of the spectrum.
B. Cosmic background radiation appears uniform across the sky.
C. The amount of helium in the universe matches predictions.

_____ Nucleosynthesis of light elements occurred shortly after the expansion of the original ball of energy.

_____ The universe is expanding.

_____ The universe began from a single point.