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THE NATURE OF LIGHTTHE NATURE OF LIGHT
ACTIVITY
With a partner, list down all the possible sources of light.
MAYBE YOU HAVE THOUGHT OF…
LIGHT PRECEDES SIGHT
THEN WHAT IS LIGHT?
BEFORE WE DEFINE LIGHT…
Let’s talk about the electromagnetic spectrum
Trace the historical development of the theories that explain the nature of light
A REVIEW OF ELECTROMAGNETIC WAVES
These are waves produced by oscillating charges.
They can travel through a vacuum or material substance.
They are transverse in nature.
There are seven identified classes of electromagnetic waves.
THE ELECTROMAGNETIC SPECTRUM
A CLOSER VIEW ON THE EM WAVES
RADIO WAVES
These include TV signals and AM and FM radio signals.
They have the longest wavelength in the electromagnetic spectrum which may be several kilometers.
They have also the least energy in the family of EM waves.
MICROWAVES
EM waves that have wavelengths in the range of centimeters.
They are used to carry communication signals over long distances (space probes).
Also used in cooking.
INFRARED WAVES
EM waves that have wavelengths slightly longer than wavelengths of red visible light.
The warming effect of the sun is an example of infrared radiation.
Can be used to produce detailed image of objects (weather forecasting)
ULTRAVIOLET WAVES
Invisible waves that lies just beyond the violet light
Has higher energy and frequency but shorter wavelengths compared to visible light.
Has enough energy to pass through clouds.
UV can be used to kill germs and disinfect objects.
X-RAYS
EM waves with wavelengths less than 10-8 m
Highly useful in medical imaging
Contain a lot of energy that may give detrimental effects to tissues
GAMMA RAYS
EM waves with the highest energy and frequency
Shortest wavelength Most penetrating Exposure to these rays
may pose danger Can be used to treat
cancer
THE NATURE OF LIGHT
DEBATES ON THE NATURE OF LIGHT
Particle or Corpuscular Theory Wave Theory of Light Dual Nature of Light
Light behaves as a PARTICLE.
EVIDENCES FOR WAVES
THOMAS YOUNG AND THE DOUBLE SLIT EXPERIMENT
POLARIZATION OF LIGHT
EVIDENCE FOR PARTICLES
PHOTOELECTRIC EFFECT
THE DUAL NATURE OF LIGHT
LOUIS DE BROGLIE
LIGHT HAS DUAL NATURE