Section 1: What is Light?
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What is Light?
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Light is a type of energy that travels in a wave
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Light can travel in a __________________ (absence of any matter) which makes it an
___________________________ wave (EM waves)
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An EM wave consists of changing ___________________ and ______________ fields which are
_____________________ to each other as _______________ waves and perpendicular to the direction
of the wave motion
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Light not only acts as a _______________, but it sometimes acts as a stream of __________________. It
has a dual nature.
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Characteristics of particles include that light travels in straight lines and in a _____________.
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In the modern theory of light, we think of light to be a series of packets of energy (or ______________).
These packets have no mass and carry quantified amounts of energy.
How Light is Produced
There are many ways to produce light:
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___________________ (a fire).
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___________________ (a spark).
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By ____________________ an object up (an electric stove or a toaster).
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_______________________ (strike a flint and steel to produce a spark).
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All of these methods involve ____________________________ one form of energy (chemical, electrical,
thermal) into another (light).
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Electrons, and other charged particles, get too much __________________.
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To release this extra energy, they release waves of __________________.
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Because it happens at the level of individual particles, you need quantum physics to get precise.
When you heat something, the molecules ____________________.
Now, the vibrating charges in the atoms release waves of energy.
The object ________________.
A light bulb works the same, but the electricity causes the ______________________.
Fluorescent bulbs do __________________ even heat up. The energy goes straight to the
_________________________.
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The Speed of Light
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all electromagnetic radiation -- from radio waves to x-rays -- travel at the speed of light.
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In empty space this speed is approximately _________________ meters per second!
Section 2: The Electromagnetic Spectrum
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The Electromagnetic Spectrum
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The full range of the EM spectrum is called the electromagnetic spectrum
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This range includes categories such as radio waves, microwaves, and visible light.
Radio Waves
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______________________ wavelengths and _______________________ frequencies
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_______ and _______ Radio Waves
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AM waves can travel _________________ than FM waves because the wavelength is
____________________
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Radio stations encode information into radio waves by varying the waves _____________________ or
frequency, called modulation
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AM = ___________________ modulation
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FM = _________________ modulation
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More information can be encoded using this method
TV and Radio Waves
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TV signals are also carried by _______________ waves
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TV signals have ___________________ wavelengths and ________________ frequencies than
radio station waves
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Use FM waves to carry ________________ and AM waves to carry ___________________
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Waves transmitted to satellites are amplified and relayed back to ground antennae then travel
through cables to TV’s in homes.
Microwaves
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Microwaves have ______________________ wavelengths and _________________ frequencies and
carry _____________ energy than radio waves
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Microwaves are also used in ___________________ (radio detection and ranging)
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Radar is most commonly used to detect the _________________ and location of a car.
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The radar gun emits waves and those waves _____________ back off the car. The rate at which the
waves are reflected is used to calculate the speed of the car.
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Radar is also used in airplanes to help ships navigate at night and in foggy weather.
Infrared Waves
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____________________ wavelengths and _________________ frequencies than microwaves and carry
more energy
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The ____________ emits infrared rays and your skin absorbs these rays
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The particles in your skin _______________ and heat up resulting in an __________________ in
temperature
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Other objects that emit infrared waves are ___________, _______________, __________________,
___________________, and _______________! Warmer objects give off __________________ infrared
radiation that cooler objects
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Infrared waves are ________________ visible with our eyes
Visible Light
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Humans see this light as ________________
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_______________ wavelengths are seen as ____________
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__________________ wavelengths are seen as violet which carries the _____________ energy
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The range of colors is called the __________________________
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ROYGBIV when combined are seen as __________________ light
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Light bulbs and fluorescent bulbs are examples of white light
Ultraviolet Light
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Produced by the ____________
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Have ____________________ wavelengths and _________________ frequencies than visible light
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Benefits: artificial UV light is used to kill bacteria on food and surgical instruments; natural UV light from
the sun helps skin cells produce vitamin D which promotes the absorption of calcium to help keep our
bones and teeth strong
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Negative Effects: overexposure can cause sunburn, skin cancer, wrinkles, eye damage, and premature
aging of the skin
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Use sunscreen!
X Rays
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_______________ wavelengths and ________________ frequencies
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X-Rays carry a great deal of energy and can penetrate a wide variety of materials
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Too much exposure to X-Rays can damage or kill living cells
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Gamma Rays
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__________________ wavelengths and _______________ frequencies
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We are exposed to small amounts of these rays daily that do not harm us
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Gamma rays are used to treat tumors to kill the cancer cells
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Unfortunately, some healthy cells are also killed during treatment