Explain the relationship between energy, wavelength, and speed of a wave. How are elements’ atomic spectra similar to humans’ fingerprints. 11/23/2015

Reminders Wed. Nov. 24: “Model 4-useful light equations” worksheet Mon. Nov. 30: textbook #45-49 on page 166 Tues, Dec 1: Quiz: Light

Science Fair Judges Recruit judges for the Science Fair Judges must be +21 years old Judges must have a background in science – College students majoring in science – Engineers

Science Olympiad Interested in science competitions? Join the Von Science Olympiad Team! Fill out the application by Nov 8 on the Von Steuben site!

Von Bridge Competition Date: Monday, December 15, 2014 Task: Construct a bridge that withstands the most weight. Winners: Travel to IIT and Compete against various schools. Scholarships and t-shirts may be available. Interested? Sign up with Ms. Roden in after school on Monday before December 1st, 2014

VON Homework Cafe Monday – Thursday 2:45 pm – 4:00 pm in the cafeteria Snacks and computer access available! Each time you attend, you will be entered into a raffle. Drawings are held every 2 weeks. – The more you attend, the better your chance to win gift cards, Von gear, dance tickets, etc…

H He Hg All

Sodium-23 Atom 11 p + 12 n 0 11 e -

Sodium-23 Atom Energy Level

Excitation of Hydrogen Atoms

Particle Nature of Light Matter can lose or gain energy but only in small, specific amounts Photon – A particle that carries energy that is gained or lost by an atom

Sodium-23 Atom Ground State -electrons are in a position of low energy

Excitation of Na Atom Now the atom is UNSTABL E Excited State -electrons are in a position of high energy

Excitation of Na Atom The atom becomes STABLE again Ground State -electrons are in a position of low energy

Chemist Humor Question: Why does hamburger have lower energy than steak? Answer: Because it’s in the ground state.

Excitation of Electrons Electrons exist in very specific energy levels. (ground state) And when these electrons absorb energy… They get energized up to higher levels.

Excitation of Electrons Quantum jump: happens all at once – instantaneously – because the electron can never exist between levels – not even for a second.

See how an electron dropping from the 3 rd level to the 2 nd level produced red light A 4  2 electron drop produces blue light And a 5  2 drop produces violet light Excitation of Electrons Electron quickly drops back down to lower level and gives off a distinct band of light energy.

Figure 1.

Ionization Energy (MJ/mol) Intensity Photoelectron Spectra for Oxygen AB C

Parts of a Wave crest node / origin trough wavelength Amplitude

Parts of a Wave Wavelength, λ – The distance between crests on a wave – Units = m, cm, nm

Parts of a Wave A B C Low High Medium

1.What is the wavelength of a wave that has frequency of 3.44 x 10 9 Hz? 2.Light reflected from a green leaf has a wavelength of 4.90 x m. What is the ν of the light? 3.What is the energy of a wave with a of 5.89 x m?

What is the wavelength of a wave that has frequency of 3.44 x 10 9 Hz? 1.Write the givens. 2.Write the formula. 3.Manipulate formula to find the unknown.

Light reflected from a green leaf has a wavelength of 4.90 x m. What is the frequency of the light? 1.Write the givens. 2.Write the formula. 3.Manipulate formula to find the unknown.

Light reflected from a green leaf has a wavelength of 4.90 x m. What is the frequency of the light? 4.Substitute in known values and solve. 5.Make sure units are correct.