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The term “Light” can describe many different forms of electromagnetic energy. Light is Energy. Electromagnetic Spectrum. increasing frequency. increasing wavelength. Electromagnetic Spectrum. Long wavelength --> small frequency Short wavelength --> high frequency.

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Presentation Transcript
electromagnetic spectrum1

increasing frequency

increasing wavelength

Electromagnetic Spectrum

Long wavelength --> small frequency

Short wavelength --> high frequency

the visible spectrum
The Visible Spectrum

COLOR FREQUENCY (Hz) WAVELENGTH (nm)

  • Red 4.04.8 x 1014 700-630
  • Orange 4.85.1 x 1014 630-590
  • Yellow 5.1-5.4 x 1014 590-560
  • Green 5.4-6.1 x 1014 560-490
  • Blue 6.1-6.7 x 1014 490-450
  • Violet 6.7-7.5 x 1014 450-400
electro magnetic spectrum
ElectromagneticSpectrum

In increasing energy, ROYGBIV

nature of light
Nature of Light

Like sound waves, light exhibits properties of waves.

These are diffraction, reflection, refraction and interference.

In addition, light waves also exhibit dispersion and polarization.

Unfortunately, Light cannot be completely described by

the Wave theory.

nature of light1
Nature of Light

Light has particle-like

properties as shown by

Einstein's Photo-electric effect.

Light is said to travel in photons

or small packets of NRG.

The Explanation  Dual-nature of light

the principle of reflection
The Principle of Reflection

The Angle of Incidence = The Angle of Reflection

mirror image
Mirror Image

Image formation from a plane mirror

Image appears at a

distance equal to the

object distance.

Image is the same

size as the object.

refraction
Refraction

The bending of light upon entering a medium with

with a different density.

A light wave will speed up or slow down in response to a changing medium.

beach party
Beach Party

Imagine lines of people rushing from the parking lot to the sandy beach. People can run faster on pavement than in the sand.

Pavement

Sand

beach party1
Beach Party

Pavement

Sand

beach party2
Beach Party

Pavement

Sand

beach party3
Beach Party

Pavement

Sand

beach party4
Beach Party

As people enter the sand, they slow down.

Pavement

Sand

beach party5
Beach Party

Pavement

Sand

beach party6
Beach Party

Pavement

Sand

refraction1
Refraction

Light waves, like people waves, will slow down and bend or refract.

refraction2
Refraction

Incident

Angle

As a wave enters a piece of glass its velocity slows down and the wave is bent towards the normal line. As it exits it will speedup and is bent away from the normal line.

Air

Glass

medium

Surface Normal

dispersion
Dispersion

Light of different frequencies is refracted by different amounts

Red Light (lower frequency, longer wavelengths) is bent the least.

Blue Light (higher frequency, shorter wavelengths) is bent the most.

Refraction is Dispersive

wave speed
Wave Speed

v = l Sound (in air) ~ 344 m/s

Light (in vacuum) ~ 3x108 m/s

What is the wavelength of a sound wave which has a frequency of = 1000 Hz?

344 m/s = l 1000 Hz

l = 344m/s/1000/s (Seconds cancel)

l = 0.34 meters

1/3 of a meter in size, 1000 of them each second!

wave speed1
Wave Speed

c = l Sound (in air) ~ 344 m/s

Light (in vacuum) ~ 3x108 m/s

What is the wavelength of a radio wave with = 94.1 FM?

AM kHZ = 103 Hz

FM MHz = 106 Hz

3x108 m/s = l (94.1 x 106 Hz)

l = 3x108 m/s / 94.1 x 106 /s

l = 3.2 meters

3 meters in size, 94,100,000 of them each second!