1. Observing Atomic Spectra Wave simulation Bohr’s Model of the Atom

2. Electromagnetic Waves Light is an electromagnetic wave. Wave simulation 1.label wavelength 2.label crest, 3.label trough 4.label amplitude

3. Electromagnetic Waves Light is an electromagnetic wave. The wavelength of a wave is the measure of how long the wave is, or how far it is from one crest to the next crest. 1.label wavelength 2.label crest, 3.label trough 4.label amplitude

4. Electromagnetic Waves The wavelength of a wave of electromagnetic radiation determines what color we see when observing that wave. Our eyes are able to distinguish between very small differences in wavelengths. Red Light Blue Light Wavelength 725 nm 465 nm 0.000000725 m 0.000000465 m

5. Electromagnetic Waves ColorWavelength (nm) Red780-622 Orange622-597 Yellow597-577 Green577-492 Blue492-455 Violet455-390

6. Determine the wavelength of light based on its relative color Calculate the frequency and energy of a photon of light Chapter 13.3 Notes Electrons and Light

7. Electromagnetic Waves Light is an electromagnetic wave. A wave has several key properties that we can measure; the length of the wave (wavelength), the height of the wave (amplitude), and the frequency of the wave. 1.label wavelength 2.label crest, 3.label trough 4.label amplitude

8. Electromagnetic Waves Light is an electromagnetic wave. The frequency of a wave is the number of waves that pass you in a given amount of time. Frequency is measured in cycles per second (1/s). 1.label wavelength 2.label crest, 3.label trough 4.label amplitude

9. Each of these two waves are passing by you at the same speed. If you counted how many waves passed by you each minute, which wave would have a higher number (higher frequency)? _______ would have a higher frequency. Which wave has a shorter wavelength? _______ has a shorter wavelength. Write a sentence describing the relationship between the wavelength and frequency of a wave. Electromagnetic Waves

10. The product of the frequency (f) and wavelength (λ) of wave can be used to calculate the speed of the wave. speed of a wave = f x λ Electromagnetic Waves

11. Practice Problem #1 A sound wave with a measured frequency of 512 s -1 and a wavelength of 0.67m travels from a speaker to your ears. What speed is the wave traveling? The speed of sound is about 340 m/s. Electromagnetic Waves

12. Key Point! For every type of electromagnetic wave, the speed is the same. Electromagnetic Waves

13. Frequency and Wavelength formula If the speed and wavelength are known, the frequency is If the speed and frequency are known, the wavelength is: c f

14. Practice Problem #2 A wave of red light has a measured wavelength of 4.50 x 10 -7 m. Calculate its frequency. Electromagnetic Waves

15. Practice Problem #3 A wave of blue light has a measured frequency of 6.5 x 10 14 Hz. Calculate its wavelength. Electromagnetic Waves

16. All waves carry an amount of energy as they move. Think of ocean waves crashing against the shoreline, or sound waves that can damage your ear drums. The amount of energy an electromagnetic wave carries can be calculated if its frequency is known. Energy = f x h h is a constant called Plank’s constant. Its value is always 6.62 x 10 -34 Js. Energy in Waves

17. Practice Problem #4 The frequency of a light wave is 2.5 x 10 14 s -1. How much energy in J is this wave carrying? Energy in Waves

18. The “color” of light depends on the wavelength of the wave. The shorter the wavelength, the higher the energy carried by the wave. The higher the frequency, the higher the energy carried by the wave. Determine the Energy in Waves

19. The “color” of light depends on the wavelength of the wave. The shorter the wavelength, the higher the energy carried by the wave. The higher the frequency, the higher the energy carried by the wave. Determine the Energy in Waves Which wave would carry more energy?

20. 1. The wavelength of light can be estimated by observing its color. 2. The estimated wavelength can be used to calculate the frequency of the light wave. 3. The frequency can be used to calculate the energy of the light wave How to Calculate the Energy of a Wave ColorWavelength (x 10 -9 ) Red780-622 Orange622-597 Yellow597-577 Green577-492 Blue492-455 Violet455-390

21. Atoms of an element are energized in a discharge lamp and the atomic spectrum of the light is recorded. The brightest band of color in the atomic spectra was green light. Use the table below to estimate the wavelength of the light, and calculate its frequency and energy. 1. 2. 3. How to Calculate the Energy of a Wave ColorWavelength (x 10 -9 ) Red780-622 Orange622-597 Yellow597-577 Green577-492 Blue492-455 Violet455-390

22. On the back of your “Observing Atomic Spectra” Worksheet, calculate the amount of energy for each color photon you observed in Hydrogen’s atomic spectra. How to Calculate the Energy of a Wave ColorWavelength (x 10 -9 ) Red780-622 Orange622-597 Yellow597-577 Green577-492 Blue492-455 Violet455-390

23. When elements in the gaseous state are electrically stimulated, they emit a light of a specific wavelength, or color. Every element emits a different colored light. Neon = orange red Xenon = blue Argon = lavender How do Neon lights work?

24. So where exactly does the neon light come from? As electrons gain energy, they become excited and move into high energy levels around the atom. How do Neon lights work?

25. When those electrons drop back down to the original energy level, the energy is released as a photon of light. How do Neon lights work? http://phet.colorado.edu/en/simulation/discharge-lamps

26. The specific color that each element emits is called its atomic emission spectrum. This spectrum can go outside of the visible light range. How do Neon lights work?

27. Concepts

28. Atoms can absorb energy in the form of electrical or thermal energy. The electrons around the atom are responsible for absorbing the energy. Energizing Atoms

29. Before electrons absorb energy, they reside in the lowest energy state possible. This state is a as close to the nucleus as possible. Energizing Atoms

30. The lowest energy state an electron is found in is called its ground state. Energizing Atoms

31. When as electron absorbs energy, it becomes excited. The energy that the electron absorbs cause it to jump into a higher energy level. Energizing Atoms

32. An electron in a higher energy level than its ground state is in an excited state. Energizing Atoms

33. Excited electrons want to have the lowest amount of energy possible, and fall back to a position closer to the nucleus. Energizing Atoms

34. In order to fall back to their ground state, excited electrons must release the energy they absorbed. The energy is released by a falling electron as a photon of light. Energizing Atoms