The Nature of Light

Light is a Wave

• In 1801, Thomas Young passed a beam of ______ through two narrow ___________ and then onto a screen on the other side. The light ended up producing a __________ patter on the screen.

• This is called diffraction, and it is when a wave ________ and __________ out around an object or opening. Similar to water waves bending around dropped objects

• Light is a _____________ wave that moves in a direction that is carried by an ___________ field and a ____________ field in opposite directions.

• Light also carries _________ with it. Light is often referred to as electromagnetic radiation

The Photoelectric Effect

• In 1887, Heinrich _______ observed that light can knock ________ away from the _______ inside a __________

Light is a particle

• This proved that light MUST have _______________, and that it is a __________.• Light is made up of particles called ___________. These are best described as wave ____________ of light, carrying energy. They stay

together similarly to a standing wave on a jump rope

Light is both WAVE and PARTICLE• At the very tiny ___________ world of _______________, phenomena can be described in terms of properties of both ________ and

particles.• This is called the wave-particle __________.

The speed of light is: ___ * 108 m/s = 6.71 * 108 mi/h. This is the fastest observable speed in the universe

Gamma Rays

• These are released during __________ ____________, in controlled nuclear power plants• They are used to treat cancer, but can also cause cancer. These are the shortest and most energetic light waves in the universe

X-Ray• Because x-rays are as small as ________, they can be used to see through the skin. They get observed by the body’s _________.

Ultraviolet (UV)• Ultraviolet light has much _______ energy than visible light. This explains why you can often get sunburned on overcast days as well• The __________ light that filters through UV lamps is bright because of the high _________ UV waves•

VISIBLE LIGHT

Infrared (IR)• We know that objects ___________ _______ (a crowded room is a warm room). Most objects _______ most of their ________ in the

infrared spectrum of light. • So, IR lamps are very useful for temperature comparisons on objects

Microwaves• Microwaves have just enough energy to shake around ________ molecules inside of food. This allows it to cook.• Most mobile phones and _________ __________ use microwaves to transmit signals

Radio• These are the _________ and __________ energy waves• These waves can be used to _________ signals from TV, AM, FM and even be used as ________ to determine the locations of aircraft