1. Radiant Energy Objectives: 1. Describe a wave in terms of its frequency, speed, and amplitude. 2. Identify the major regions of the electromagnetic spectrum. Key Terms: electromagnetic radiation, amplitude, wavelength, frequency, speed of light, visible spectrum

2. Waves and Energy A wave is a disturbance that transfers energy through a medium. – All waves can be characterized by the following four characteristics: amplitude, wavelength, frequency, and speed. – Light travels in electromagnetic waves. Einstein called the quantum packets of energy photons. Each photon caries the exact amount of energy that the atom absorbed. – The Photon has a dual nature. (double transverse wave) – One part light and mass. Or …one part electric and one part magnetic – This dual nature allows the photon to travel through space.

3. Amplitude The maximum distance the molecules are displaced from the midline – Or... The distance from the midline to the crest or trough – As energy , amplitude  crest trough midline

4. Wavelength The distance between 2 consecutive crests or troughs – Unit is the meter or nanometer (1nm = 1x10 -9 m)

5. Frequency The number of crests of troughs passing a point per unit time – Transverse … crests(troughs)/second – Compression … compressions(rarefactions)/second Unit is the hertz (Hz) 1Hz = 1/s or s -1

6. Speed of Waves Speed in any given medium is constant. – Speed (c) = frequency (Hz)  wavelength ( ) or c = Hz x If Hz  then  or if Hz  then  – A medium is any substance or region through which a wave is transmitted. Solid, liquid, or gas – Fastest in solid & slowest in gas Transfers energy only without any net movement 2 properties of a medium affect wave speed – Density-  in density without a change in medium slows the wave – Elasticity -  elasticity speeds up a wave

7. Light Energy The atom is the source of all light. When an atom absorbs a quantum of energy its electrons (e-) become excited and jump to higher energy orbits (excited state) As the excited e- looses energy, it falls back to its original orbit (ground state) and releases a photon. – A photon is a tiny packet or bundle of energy that contains the exact amount of energy that the atom absorbed – The amount of energy a photon contains determines what type of light is emitted

8. Electromagnetic Spectrum The frequencies of light created as an atom reaches quantum requirement is called a line spectrum. – a line spectrum (or emission spectrum)contains only certain frequencies of light which can be seen by passing the emitted light through a prism

9. Plank’s Equation Plank's theory states that each element can only absorb a certain amount of energy (quantum) therefore it can only emit a limited amount of energy. Each element absorbs energy only when the quantum is reached. This was further explained by the equation: Plank used this concept to describe why certain elements give of different color lights emit different colors. E = hv Plank’s Constant 6.6262 x 10 -34 Frequency Hz Quantum energy requirement if you know the amount of energy absorbed you can calculate the wavelength using the formula for wave speed (c = v x )