Which of the following lasers emits photons with the lowest energy? a. an Ar* la

Question

Which of the following lasers emits photons with the lowest energy? a. an Ar* laser with lambda = 514.5 nm b. a He-Ne laser with lambda = 633 nm c. a Kr^+ laser with lambda = 647 nm d. a Nd: YAG laser with lambda = 1064 nm e. an ArF laser with lambda = 193 nm Which of the following statements about energy, systems, and surroundings is NOT true? a. The system can do work on the surroundings. b. The surroundings can provide thermal energy to the system. c. The system can be a chemical reaction that occurs in a sample of matter. d. The system is the part of the universe that is the focus of thermochemical study. e. The surroundings experience the same energy change as the system in order to keep the total energy in the universe constant. Bond length and bond strength are _____ a. arbitrary. b. unrelated. c. inversely proportional. d. identical. e. directly proportional. Which type of bonding involves the sharing of valence electrons by two atoms? a. polar ionic b. metallic c. covalent d. ionic e. intramolecular

Explanation / Answer

11. B) In a helium neon laser, a low pressure mixture of helium and neon (<15%) is contained in a narrow bore glass tube. A longitudinal, DC electrical discharge is maintained in the narrow tube. This creates a plasma. Collisions with free electrons in the plasma excite the helium atoms and cause a significant number of them to be trapped in the lowest-energy metastable states.

12. e) surrounding experience the same energy as the system in order to keep the total energy in the universe constant

13. C) bond length and bond strength are inversely related

14. c) covalent bond

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