CH. 35 Light

Kennesaw State UniversityPhysics 2212

Light• Energy of a photon:

h = Planck’s constant = 6.63 x 10-34 J.s

• Light has dual nature (wave/particle)

E=h f

Light Particle Nature

http://www.sciencemag.org/content/338/6114/1576.full

(Example) Photoelectric Effect:

Huygens’s Principle

“Any wave front can be taken as a series of point sources for the wave propagation”

Other Characteristics of Light

• Light is quantized like charge• Frequency and wavelength can change and

relate via equation:

• Light has speed (“c”) of 3.00 x 108 m/s

c=λ f

Electromagnetic Spectrum

Speed of Light

• In a vacuum:

• In a medium:

Where n = index of refraction Example: nvacuum=1 nair=1.01

c=v

v= 𝑐n

Snell’s Law

• Snell’s Law of Refraction Equation:𝑛1sin𝜃1=𝑛2sin𝜃2

Snell’s Law Critical Angle

sin𝜃c=𝑛rni