Wavelength, Frequency, & Energy of Light

Byno Chemistry 2013

Why does Aluminum not burn? Why does Alcohol burn but it will not

react with anything else? Why does Aluminum react with

Hydrochloric Acid? Why does Calcium Carbonate react with

vinegar, but it doesn’t burn?

Discuss in your group

Identify and use the symbols for frequency and speed of light

Use 3x108 m/s as the value for the speed of light

Calculate E = hv using Planck’s constant Calculate c = λv using the speed of light

I can . . .

Symbol Meaning Value or Unit

c Speed of light 3x108 m/s

h Planck’s constant 6.63 x 10-34 Js

E Energy Joules (J)ν frequency Hertz (Hz)λ wavelength Nanometer (nm)

Symbols

Visible light breaks into a spectrum of colors depending on the wavelength of the light

Visible Light

Spectroscope

A spectroscope is a device used to separate the colors of visible light and measure their wavelengths

Electrons exist in the electron cloud but they can be found in distinct ‘levels’

They are the s-orbital, p-orbital, d-orbital, and f-orbital

Electrons can jump up from one orbital to the next when energy is applied to the atom

Electron Energy Levels

Ex. Cadmium

Groups 1 and 2, and Helium

S-Orbital

Groups 13-18 (except Helium)

P-orbital

Transition metals – Groups 3-12

D-orbital

Lanthinide and Actinide series – Rare Earth Metals

F-orbital

Electrons The motion of electrons in

the electron cloud of an atom creates low energy waves such as visible light and radio waves

The energy is the result of electrons hopping from one level up to the next

Energy is emitted when the electron falls back to the original level

An element can react with another element if it has electrons that can move

When a chemical substance reacts with another, the electrons move and give off energy in the form of light

Reactivity

The energy of the electron’s movement in a chemical reaction can be calculated

Wavelength

Speed of light (m/s)

Wavelength

(m)

Frequency (Hz)

Example: A helium laser emits light with a wavelength of 633 nm. What is the frequency of the light?

Now that we know the wavelength, we can calculate the energy of the electron

Energy

Energy

(J)

Frequency

(Hz)

h (Planck’s Constant)6.63 x 10-34

Js

Example: A helium laser emits light with a wavelength of 633 nm. What is the energy of its electrons? We previously

calculated frequency = 6.00 Hz

What is the energy of light whose wavelength is 4.06 x 10-11 m?

Practice

c÷λ = νν = 3.8x108 m/s ÷ 4.06x10-11 mν = 7.39x1018 Hz

E = h × νE = 6.63x10-34 Js × 7.39x1018 HzE = 4.9x10-15 J