Bouncing Beams and Sticky Glass

5.2.2 EM Wave Phenomenon

Reflection

• Waves that change mediums or hit boundaries obey the Law of Reflection.

• Angles are always measured from the normal!

Equation

ri

θi θr

incidentray

reflectedray

normal

Refraction

• Fast Slow = away from normal

• Slow Fast = toward normal

Equation

Snell’s Law2211 sinsin nn

θr

incidentray

reflectedray

normal

θ2

refractedray

n1

n2

θi or θ1

Refraction• Wavelengths change with corresponding differences in

speed.

Equation

2

1

2

1

1

2

vv

nn

Refraction (Special Cases)- Special cases in which no bending occurs…

- Two mediums with the same index of refraction.

- A ray entering another medium at an angle of 0°

corn oilglycerol

airdiamond

n1sinθ1 = n2sinθ2

1.47 sinθ1 = 1.47 sinθ2

θ1 = θ2

n1sinθ1 = n2sinθ2

1.0 sin 0° = 2.42 sinθ2

0 = 2.42 sinθ2

θ2 = 0°

A ray of light with a frequency of 5.09 x 1014 hertz moves from air into flint glass. The angle with which the ray strikes the surface of the flint glass is 40° away from the normal. Which is the faster medium? Determine the angle of refraction. Draw the refracted ray.

airflintglass

n1sinθ1 = n2sinθ2

1.00 sin 40° = 1.66 sinθ2

θ2 = 23°

air is faster (lower index)

Example

The Wave Nature of Light• Consider each of the 8 phenomenon. Which of them

could be demonstrated with light? Which are PROOF that light has a wave nature? Which can also occur with particles?

ReflectionWorks with BOTH particles and waves.

NOT proof that light is a wave.

Interference

ONLY occurs with waves.

Supports wave model of light.

Standing WavesWaves ONLY.

Lasers – supports wave model.

ResonanceWaves ONLY.

Lasers – supports wave model

Doppler EffectWaves ONLY.

Red shift/Blue shift – supports wave model.

Diffraction

Waves ONLY.

Supports wave model.

RefractionDoes not DIRECTLY support

wave model.

PolarizationWaves ONLY.

Supports wave model.

Double Slit ExperimentThomas Young’s double slit experiment is the best demonstration

of light’s wave nature as it combines both diffraction and interference.

End of 5.2.2 - PRACTICE