Do Now 1 Label the parts of a

Do Now: 1. Label the parts of a wave: 2. Why do waves with long wavelengths have low frequencies? 3. Would gamma rays (very high frequencies) have very little energy or lots of energy? 4. What color of visible light (ROYGBIV) has waves with the highest frequencies? Longest wavelengths? Least energy?

• • Review equations c= λ ν E=hν E = hc / λ *h = Plack’s constant = 6. 626 x 10 -34 J*s c=speed of light = 3. 00 x 108 msec

Objectives: The interaction of electromagnetic waves or light with matter is a powerful means to probe the structure of atoms and molecules.

If the entire electromagnetic spectrum were stretched out to the length of the United States, the piece that would be visible to human eyes would be the size of a dime.

Electromagnetic Radiation: ? ? it ? s i t a h W All forms of EM radiation can be described in terms of an oscillating electrical and magnetic field. (waves!) Practice: Microwaves in the US operate at a frequency of 2. 45 GHz. What is the wavelength of this radiation?

Energy

Quantization and Planck’s Equation: Planck found a relationship between energy and the frequency of electromagnetic radiation. His equation … E=hv It is observed that matter only emits certain energies! Quantization: only certain energies are allowed

Quantization and Planck’s Equation: Planck found a relationship between energy and the frequency of electromagnetic radiation. His equation … Quantization: only certain energies are allowed These quantized, packets of energy, can also be thought of as VERY tiny particles called photons. (this revises Planck’s equation)

Quantization and Planck’s Equation: Practice: A CD player emits a red light with a wavelength of 685 nm. How much energy does 1 photon of this light have? For 1 mole of photons?

In summary: 1. EM radiation is a broad energy spectrum whose wave-like properties can be described by the equation _____ and whose particle-like energy can be described by the equation _____. Objectives: • The interaction of electromagnetic waves or light with matter is a powerful means to probe the structure of atoms and molecules.

Try It: Complete #’s 2, 4, 6, 8 and 9