Discussion Activity

DISCUSSION ACTIVITY for WEEK 10

Name _________________________

LEARNING CATALYTICS GROUP REVIEW (5-10 min)

THE PLAN:  Lasers are becoming an important tool in medical procedures.  We are going to explore lasers for the removal of tattoos and use concepts from chapter 6 (energy from photons, electronic configurations, quantum numbers) to explore how lasers work and the components of tattoo ink.

The learning objectives for today’s session are for you to (relationship to learning objectives (LO) from lecture are in parentheses):

• Calculate energy, wavelength, or frequency of electromagnetic radiation given appropriate information.(Chapter 6 LO C)
• Given the electromagnetic spectrum, rank the common types of radiation according to their wavelengths or energy. (Chapter 6 LO D)

We will also:

• Draw and/or recognize the shapes and nodes of s, p, and d orbitals. (Chapter 6 LO Q)
• Determine quantum numbers and assign sublevel designations for orbitals that exist for n = 1, 2, 3, and 4. (Chapter 6 LO R)
• Use the periodic table to write condensed electron configurations. (Chapter 6 LO U)

We encourage students to work with their teams to complete as much of the activity as you can as a group, but each student will submit their own work on gradescope.

THE LASER (30-35 min)

You should have watched the youtube video about tattoo removal ().  Take the first few minutes to talk about what you learned from the video and then work together to answer the questions below.  One member of the group should write down the responses to these questions on a sheet of notebook paper or digitally.  This paper will be turned into the instructor at the end of class or submitted on ICON.

1. Explain the process of removing a tattoo using a laser.  How does this work?
   
   
   

1. Different lasers are used to remove different inks.  For example, a 694 nm ruby laser can remove blue and green ink, but a neodymium yittrium aluminum garnet (Nd-YAG) laser with wavelengths of 1064 and 532 nm are used for black, brown, orange, yellow, and red inks.  Calculate the frequency of light for each of these wavelengths.
   
   
   

1. Calculate the energy of a photon emitted from each of the lasers in Question 2 and rank them in order of lowest to highest energy.

1. Why would you choose different lasers for different color inks?
   
   
   
   
   

1. The laser emits light because electrons in the material are excited (by applying electricity) from the ground state to an upper excited state.  

1. Draw your own diagram that illustrates this process.  
   
   
   
   
   
   
   
2. Using the energies from question 3, describe the differences in the energy gap between the ground state and excited state in the different lasers.
   
   

1. Using the ruby laser, the doctor would apply with an energy of 4 J/cm2 to a spot size of 8 mm2 (Ramsey, Semin. Plat. Surg. 2007, 21, 175-192).  How many photons are being emitted from the laser?
   
   
   
   
   
   
   
   
2. What are the consequences of putting that much energy into the surface of the skin?  What are some of the side effects of this procedure?
   

REFLECTION

An important part of developing skills that are important for supporting your learning (and that are highly valued by employers) is to assess your progress and identify areas where you can improve. Reflect on your critical thinking so far today, particularly the way in which you synthesized information.

• Circle the number on the rubric you think best characterizes your level of critical thinking on this activity.

• Write a brief summary of why you gave yourself this rating. Provide specific evidence an observer would have seen to support this rating.

• Identify one area where you think you can improve your performance next week.
  
  

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