Gloucester County Institute of Technology



Classwork and Homework

Light and Waves

Classwork:

1. According to Einstein’s view of matter and energy, what is the common link between light and matter?

2. What is Chemistry?

3. How does diffraction effect the double slit experiment?

4. The wavelength of light emitted from a traffic light having a frequency of 6.15 *1014 Hz is _________.

5. An electromagnetic wave has a frequency of 6*105 Hz. What is the wavelength?

6. An electromagnetic wave has a wavelength of 5*10-13 m. What is the frequency?

7. An electromagnetic wave has a frequency of 9*10-7 Hz. What is the wavelength?

8. What is the frequency of yellow sodium light that has a wavelength of 579nm?

9. Electromagnetic radiation with a wavelength of ________ nm appears as green light to the human eye. The frequency of this light is 5.71 x1014 Hz.

10. Explain Newton’s original ideas about the nature of light.

11. While standing in a room with two speakers (speakers A and B), each emitting sound with a wavelength of 2m, you notice you cannot hear the sound. Compared to the closer speaker, what’s the smallest difference in distance to the further speaker (ignore reflection of sound off of walls etc).

12. While standing in a room with two speakers (speakers A and B) centered about the center of the room, pointed at the wall. You notice you cannot hear the sound while standing 1 meter from the center of the far wall. What’s the next distance from the center you could stand at that would you to hear the sound at its loudest?

Homework:

13. How are matter and energy related?

14. Why is the understanding of energy and matter vital to one’s understanding of Chemistry?

15. How does interference effect the double slit experiment?

16. A radio station broadcasts at 101.5 MHz. The wavelength of the signal is __________ m.

17. An electromagnetic wave has a wavelength of 1.5 nm. What is the frequency?

18. An electromagnetic wave has a wavelength of 5*10-13 m. What is the frequency?

19. An electromagnetic wave has a wavelength of 300 m. What is the frequency?

20. What is the frequency of orange lithium light that has a wavelength of 650nm?

21. An FM radio station broadcasts electromagnetic radiation at a frequency of 99.5 MHz. The wavelength of this radiation is __________ m.

22. What is the frequency, in Hz, of electromagnetic radiation that has a wavelength of 0.55 m?

23. What is the frequency of light, in Hz, that has a wavelength of 1.23 x 10-6 cm?

24. What is the wavelength of light (nm) that has a frequency of 3.22 x 1014 Hz?

25. What is the wavelength of light (nm) that has a frequency 4.25 x 1014 Hz?

26. Explains Hyugen’s original ideas about the nature of light.

27. How are the properties of fluids in a tank, sound from a set of speakers, and light passing through a double slit all related to one another?

28. While standing in a room with two speakers (speakers A and B) centered about the center of the room, pointed at the wall. You notice you cannot hear the sound while standing 1 meter from the center of the far wall. What’s the next distance from the center you could stand at that would still prevent you from hearing the sound.

Planck’s Quantum Hypothesis

Classwork:

29. What is the energy of a photon that has a frequency of 7.0 x 1015 Hz?

30. What is the energy of a photon that has a frequency of 4.5 x 1015 Hz?

31. What is the energy of a photon that has a wavelength of 720 nm?

32. Electromagnetic radiation with a wavelength of 531 nm appears as green light to the human eye. The energy of one photon of this light is 3.74 x10-19 J. Thus, a laser that emits 2.3 x10-2 J of energy in a pulse of light at this wavelength produces __________ photons in each pulse.

33. The wavelength of a photon that has energy of 5.65 x 10-19 J is __________ nm.

Homework:

34. What is the frequency (Hz) of a photon that has energy of 4.38 x 10-18 J?

35. The energy of a photon that has a frequency of 7.75 x 1014 Hz is __________ J.

36. What is the energy of a photon that has a wavelength of 450 nm?

37. Electromagnetic radiation with a wavelength of 525 nm appears as green light to the human eye. The energy of one photon of this light is __________ J.

38. The energy of a photon that has a wavelength of 10.0 m is __________ J

Wave Nature of Matter

Classwork:

39. What implication does the equation ρ=h/λ have on how we view matter or anything with momentum.

40. What is the wavelength of an electron which has a velocity of 3.5 x 107 m/s?

(me = 9.11*10-31 kg)

41. The de Broglie wavelength of a12.0 gram bullet traveling at the speed of sound is _________ m. The speed of sound is 331 m/sec.

42. The de Broglie wavelength of an electron with a velocity of 6.00 x106 m/s is __________ m. (me = 9.11*10-31 kg)

43. What is the wavelength of an electron which has a velocity of 6.0 x 107 m/s?

(me = 9.11*10-31 kg)

Homework:

44. Why would the dual nature of matter make it difficult to observe very small particles like electrons?

45. What is the wavelength of an electron which has a velocity of 1.2 x 108 m/s?

(me = 9.11*10-31 kg)

46. The de Broglie wavelength of a10.0 gram whip traveling at the speed of sound is _________ m. The speed of sound is 331 m/sec.

47. The de Broglie wavelength of an electron with a velocity of 1.30 x107 m/s is __________ m. (me = 9.11*10-31 kg)

48. What is the wavelength of an electron which has a velocity of 4.0 x 107 m/s?

(me = 9.11*10-31 kg)

History of the Atom

Classwork:

49. Why do neutral atoms have the same numbers of protons and electrons?

50. What about electrons allow them to be some of the fastest traveling sub atomic particles?

51. Why was it important to use alpha particles in order to discover the neucleus, as opposed to gamma rays or beta particles?

52. Based on Bohr’s model of the atom, why do you think electrons were the first subatomic particle to be discovered?

Homework:

53. Based off of the first experiments into the composition of atoms, why were neutrons the last particles to be discovered?

54. As more and more protons enter the nucleus of an atom, increasing ratios of neutrons are needed. Why do you think this is?

55. Why is it not possible for an electron to continue in a set orbit around the nucleus like a planet around the sun?

56. Explain how emission spectra of gasses helped scientists to determine electrons traveled in energy levels.

57. Give one example of black body radiation that you see in your everyday life.

Bohr’s Atomic Model

Classwork:

58. The binding energy of the hydrogen atom in its ground state is -13.6 eV. What is the energy when it is in the n = 4 state?

59. What is the energy of the second excited state (n=3) of hydrogen?

60. What is the energy of the ground state (n=1) of hydrogen?

61. How much energy does an electron in hydrogen need as it jumps from ground state to the second excited state?

62. If an electron returns from the second excited state to ground state, what 3 Energies of photons could it emit?

63. If an electron returns from the second excited state to ground state, what 3 frequencies of photons could it emit?

64. A Hydrogen electron drops from its sixth excited state back down to its forth excited state.

a. What are the n values associated with these two states?

b. How many different types of photons can it emit?

c. What is change in energy (in eV) associated with each transition?

d. What is the frequency associated with each of the emitted electrons?

e. What is the wavelength associated with eachof the emitted electrons?

f. What possible types of electromagnetic radiation are given off during this transition?

Homework:

65. In state n = 1, the energy of the hydrogen atom is -13.58 eV. What is its energy in state n = 2?

66. The wavelength of a ruby laser is 694.3 nm. What is the energy difference (in eV) between the two energy states involved in laser action?

67. If an electron returns from the second excited state to ground state, what 3 wavelengths (in nm) of photons could it emit?

68. If an electron returns from the second excited state to ground state, what 3 types of EM Radiation could it emit (if visible light is emitted, include the color)?

69. The electron of a hydrogen atom makes a transition from the n = 5 state to the n = 2 state. What is the wavelength of the emitted photon?

70. A Hydrogen electron drops from its forth excited state back down to its first excited state.

a. What are the n values associated with these two states?

b. How many different types of photons can it emit?

c. What is change in energy (in eV) associated with each transition?

d. What is the frequency associated with each of the emitted electrons?

e. What is the wavelength associated with eachof the emitted electrons?

f. What possible types of electromagnetic radiation are given off during this transition?

Answers

1) They are two forms of the same thing linked by the equation E=mc2

2) The study of matter and the changes it undergoes.

3) Because of diffraction, two slits behave as two unique wave sources in perfect synchronization.

4) 4.87x10-7 m or 487 nm

5) 500 m

6) 6*1020 Hz

7) 3*1014 m

8) 5.18*1014 Hz

9) 525 nm

10) Based off of Newton’s observation, light behaved like a beam of particles. It bounced off of surfaces with given angles and therefore must be made of particles.

11) 1m

12) 2m

13) Matter is another form of energy. The two share similar properties. Both are particles and waves and one can be transferred into another

14) Chemistry is the study of matter and how it changes. Matter IS energy. Energy is required to cause any type of change.

15) Interference between two in sync waves is what is responsible for the reoccurring pattern of light and dark bands due to the interference of crests and troughs in waves.

16) 2.956 m

17) 2.0*1017 Hz

18) 6*1020 Hz

19) 1*106 Hz or 1MHz

20) 4.6*1014 Hz

21) 3.02 m

22) 5.5*108 Hz

23) 2.44*1016 Hz

24) 932 nm

25) 706 nm

26) Huygens’s thought that because light from far away object could be observed from seemingly everywhere it was easier to consider that light was a wave. Otherwise, Huygens’s argued, an infinite number of particles would need to be created by something like a star, requiring an infinite amount of energy.

27) Since waves are all similar, all of these systems involve the movement of waves and are therefore analogous.

28) 3 m or -1 m

29) 4.6*10-18 J

30) 3.0*10-18 J

31) 2.7*10-19 J

32) 6.1*1016

33) 352

34) 6.61*1015 Hz

35) 5.14*10-19

36) 4.4*10-19 J

37) 3.79*10-19

38) 1.99*10-26

39) Anything with momentum has a wavelength and is therefore a wave. Since all matter must have mass and is moving to some extent this means all matter has the qualities of a wave.

40) 2.1*1011 m

41) 1.67*10-34 m

42) 1.21*10-10 m

43) 1.2*10-11 m

44) Observing these particles with something like light would cause constant interference between the wave properties of the particles and the wave nature of light, making them impossible to observe.

45) 6.1*10-12 m

46) 2.00*10-34 m

47) 5.60*10-11 m

48) 1.8*10-11 m

49) In order to have a balanced charge, the protons and electrons must be equal since they are the only sources of + and – charge (respectively) in the atom.

50) Because electrons have the smallest mass of the classic 3 subatomic particles they require less energy to move at higher velocities. Therefore it is relatively easy to get these electrons moving very fast.

51) Since alpha particles are the only form of radiation that is positive and has a mass it would be the only particle that would bounce off of a positive nucleus.

52) Since they are located on the outside layer of the atom they are the particles that readily interact with other things outside of the atom. These particles naturally would have been discovered first because of this.

53) The first experiments done on atoms all depended on electro-magnetic interactions. Since neutrons are neutral, they would not have shown up in any tests done on to detect charged particles.

54) Since protons are positive and like charges repel one another, another type of particle is needed to keep the protons apart from one another while still binding them to the nucleus.

55) Because the electrons would need to continually radiate energy because they would have to be accelerating all the time in order to keep them from colliding with the positive nucleus.

56) Since only specific frequencies of light were emitted in these experiments, scientists could determine that only specific quantities of energy were being given off. It was noticed that there was a reoccurring pattern in these energies that corresponding to energy gaps between energy levels.

57) One such example might be Incandescent Light Bulbs

58) -0.85 eV

59) -1.51 eV

60) -13.6 eV

61) 10.2 eV

62) 10.2 eV, 1.88 eV, 12.1 eV

63) 2.46*1015 Hz, 4.54*1013 Hz, 2.92*1015Hz

64)

a. n=7,5

b. 3

c. 0.10 eV, 0.16 eV, 0.26eV

d. 2.42*1013 Hz, 3.86*1013 Hz, 6.28*1013 Hz

e. 1.24*10-5 m, 0.777*10-5 m, 0.478*10-5 m

f. They are all infrared photons

65) -3.395 eV

66) 1.79 eV

67) 122 nm, 6600nm, 103nm

68) UV, IR, UV

69) 435 nm

70)

a. n=5,2

b. 6

c. 2.86 eV, 0.967 eV, 0.306 eV, 2.55 eV, 0.661 eV, 1.89 eV

d. 6.90*1014 Hz, 2.34*1014 Hz, 7.39*1013 Hz, 6.16*1014 Hz, 1.60*1014 Hz, 4.56*1014 Hz

e. 435 nm, 1280nm, 4060nm, 487 nm, 1880 nm, 657 nm

f. Violet Light, IR, IR, Blue Light, IR, Orange Light

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