Light

Photons

Light energy that comes in tiny bundles

Lowest energy photons

Dull red color

Highest energy photons

Deep violet color

Properties of Light

Light travels in straight lines

Light ray

Narrow beam of light that travels in a straight line

We see things because…

They reflect light into our eyes

Reflection

Occurs when light bounces off a surface

Law of Refelction

Angle of incidence=Angle of reflection (mathematically represented as 0_i=0_r)

Normal Line

At the point of incidence where the ray strikes the mirror, a line drawn perpendicular to the surface of the mirror or the boundary between mediums

Refraction

Occurs when light bends when crossing a surface or moving through a material (bending). Light changes speed and bends

Medium

The material a light wave travels through (just like sound waves)

Light can change speed based on the medium it travels through. When is light fastest?

Through a vacuum

When is light slower?

Through air, water, and much slower through diamonds

As the density of a medium increases…

The speed of the light ray decreases and vice versa

When does light bend?

At the boundary between two mediums (after it bends, it continues in a straight line)

Traveling into a more dense medium…

Light refracts towards the normal

Traveling into a less dense medium…

Light refracts away from the normal

FST

Fast-Slow-Towards

SFA

Slow-Fast-Away

What does the difference between 0_i and 0_r tell us?

How many degrees a light ray has bent

What is the cause of refraction?

A change in speed

More Dense

More Bending

Index of Refraction Value

A value is assigned to a material based on the number of times slower light travels through it compared to a vacuum (value of 1.0000)

Snell’s Law

The relationship between the sines of 0_i and 0_r

Total Internal Reflection (TIR)

This occurs when an incident ray reflects, as opposed to refracts, off of the boundary between two mediums

TIR takes place when…

A light ray is more dense medium and approaching the less dense medium. The angle of incidence for the light ray is greater than the so-called critical angle

Critical Angle

The angle of incidence that provides an angle of refraction of 90-degrees

Electromagnetic Spectrum

Wide range of electromagnetic waves with different wavelengths and frequencies. They have different names but all travel at the same speed in empty space, the speed of light.

Frequency increases as…

Wavelength decreases

Most waves are not visible except…

Visible light

When are EM waves produced?

When electric charges vibrate or accelerate

Where can EM waves travel?

Through a vacuum (empty space) or through matter

Speed of light in a vacuum

3.00×10⁸ m/s

EM spectrum includes…

Radio waves, microwaves, infrared rays, visible light, UV rays, X-rays, and gamma rays

Radio Waves wavelength and frequency

Longest Wavelength

Lowest Frequency

What are radio waves used in?

Radio,

-Amplitude modulation

-Frequency modulation

TV technologies

Radar

-Send out short bursts of radio waves that bounce off objects & return to receiver

Microwaves Wavelength and Frequency

Shorter wavelength than radio waves

Higher frequency than radio

What do microwaves do?

Only penetrate food at the surface

What are infrared rays used for?

A source of heat and to discover areas of heat difference
You can’t see infrared radiation but your skin feels its warmth

Visible Light

The colors that are visible to us

What do UV Rays do?

Helps skin produce Vitamin D, can cause sunburn, cancer, and used to kill microorganisms

What do X-rays do?

Used in the medicine industry and transportation to make pictures of the inside of solid objects.

Absorbed by solid objects, so solid objects appear white

Gamma Rays Wavelength and Frequency

Shortest Wavelength

Highest Frequency

What are Gamma rays used for?

Use in the medical field to kill cancer cells, make pictures of the brain, and in industrial situations as an inspection tool