Light
What is light?

https://www.strawpoll.me/20086756

https://www.youtube.com/watch?v=7u_UQG1La1o&t=121s
Electromagnetic Waves

Lights are electromagnetic waves. They are made up of magnetic field and
electric field.
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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.
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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
Diffraction

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
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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.
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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.
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Lenses
Eyes Vs Camera