Uploaded by Piyapong Rahut


What is light?
Electromagnetic Waves
Lights are electromagnetic waves. They are made up of magnetic field and
electric field.
They travel at 300,000 km/sec
Electromagnetic Spectrum
Reflection of Light
When light hits on the surface, it bounces off and
creates a reflection pattern.
For smooth surface, the angle of incident is equal to
angle of reflection.
Refraction of Light
When light passes through from medium to another medium, the speed of
light changes.
V = ƛf
When light pass through a medium, the frequency does not change but the
wavelength and speed changes.
Snell’s Law
Refractive Index
Speed of light in air is 300,000 km/s
Critical Angle
Convex lens
Bending of the light when it pass through a gap.
Ultraviolet on Glass
When ultraviolet hits molecules of glass, vibration of electrons will have high
amplitude. They can hold energy for longer period of time.
Energy is passed onto neighboring molecules by collision.
It gives up energy as heat.
UV light cannot pass through.
Visible light on Glass
Lower frequency such as visible light, when hit glass, electrons vibrates at
lower frequency. They cannot hold energy for long time.
Less collision so less transfer of heat.
The frequency of the reemitted light that is passed from atom to atom is
identical to the frequency of light that produced the vibration in first place.
Infrared on Glass
The light causes the whole atom to vibrate. The vibration increases the
internal energy and temperature of the structure.
They are often called as heat waves.
Transparent Materials
 Objects
that allow light to pass through is
called transparent.
 Electrons
 Each
are connected to nucleus like spring.
spring will vibrate at their own
frequency, they are called natural frequency.
Eyes Vs Camera