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