Science Unit 5

The speed of light is a very important number, so it has its own symbol:

"c". This is used in equations like "E = m c2".

Within the visible light range, slightly different wavelengths are called different

"colors". The range of colors we can see is the rainbow.

Electromagnetic energy is sometimes called

"electromagnetic radiation" or "EM radiation". It is not the same as nuclear radiation, though it has a similar name.

The range of the spectrum that our eyes can see

("light") is no different from the rest of the spectrum, except for its wavelength.

What are some uses of UV rays?

- killing bacteria - phototherapy - suntanning - fluorescent lights (illumination) - uv curing

What are some uses of X-rays?

- look at bones / internal organs (medical imaging) - radiation therapy - astronomy - medical science

Starting with the lowest energy level (longest wavelength), the 7 types of EM radiation are:

- radio waves - microwaves - infrared light - visible light - ultraviolet light - x rays - gamma waves

TV Waves:

- visible light waves to eyes - radio eyes - microwaves etc.... all kinds of waves travelling all over.

Using nanometers, violet, blue, green, yellow, orange, and red light have wavelengths between

400 and 700 nanometers. (This range is just a tiny part of the entire EM spectrum, so the light our eyes can see is just a little fraction of all the EM radiation around us.)

X-ray:

A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag. Hot gases in the Universe also emit X-rays.

Spectral Signature...

A graph showing these interactions across a region of the EM Spectrum.

Is a radio wave the same as a gamma ray?

Are radio waves completely different physical objects than gamma-rays? They are produced in different processes and are detected in different ways, but they are not fundamentally different. Radio waves, gamma-rays, visible light, and all the other parts of the electromagnetic spectrum are electromagnetic radiation.

Why don't we see all the many waves constantly around us?

Because our eyes are tuned to a specific region of the EM Spectrum and can detect energy with wavelengths from 400 to 700 nanometers: the visible light region of the Spectrum.

Gamma ray:

Doctors use gamma-ray imaging to see inside your body. The biggest gamma-ray generator of all is the Universe.

For example, this leaf looks green because

EM waves interact with the chlorophyll molecules. Waves between 492 and 577 nanometers in length are reflected and our eye interprets this as the leaf being green. It basically absorbs all other colors and reflects green only so it looks green to us because that is what is being reflected to our eyes.

Objects appear to have color because

EM waves interact with their molecules. Some wavelengths in the visible spectrum are reflected and other wavelengths are absorbed.

Why is light so fast?

Electromagnetic waves are the fastest things in the universe. They travel at approximately 3.00 x 108 m/s, which means they can go 300 million meters (about 186 thousand miles) in one second.

1 cycle per second is called a

Hertz (Hz).....

Microwave:

Microwave radiation will cook your popcorn in just a few minutes, but is also used by astronomers to learn about the structure of nearby galaxies.

Why do we put telescopes in orbit?

Most electromagnetic radiation from space is unable to reach the surface of the Earth. Radio frequencies, visible light and some ultraviolet light makes it to sea level. Astronomers can observe some infrared wavelengths by putting telescopes on mountain tops. Balloon experiments can reach 35 km above the surface and can operate for months. Rocket flights can take instruments all the way above the Earth's atmosphere, but only for a few minutes before they fall back to Earth.

Infrared:

Night vision goggles pick up the infrared light emitted by our skin and objects with heat. In space, infrared light helps us map the dust between stars.

How can you use a number like "3 x 10 TO THE EIGHT POWER" in calculations?

On your calculator, look for the "EE" function. It is written in yellow above the "x-1" button. "EE" means "times ten to the power of". To make "EE", you have to press the yellow "2nd" button before the "x-1" button.

Visible:

Our eyes detect visible light. Fireflies, light bulbs, and stars all emit visible light.

What are the 7 parts of the visible spectrum? R _ _ _ _ _ _ .

ROYGBIV ..... (red, orange, yellow, green, blue, indigo, violet)

What are the names of the range of the colors?

ROYGBIV ..... (red, orange, yellow, green, blue, indigo, violet)

SEE WORKSHEET 5.3 TO LEARN HOW TO PUT IT INTO THE CALCULATOR!!!!!

SEE WORKSHEET 5.3 TO LEARN HOW TO PUT IT INTO THE CALCULATOR!!!!!

Long wavelengths of electromagnetic energy can carry

TV signals.

Each of these three quantities for describing EM radiation are related to each other in a precise mathematical way. But why have three ways of describing things, each with a different set of physical units?

The short answer is that scientists don't like to use numbers any bigger or smaller than they have to. It is much easier to say or write "two kilometers" than "two thousand meters." Generally, scientists use whatever units are easiest for the type of EM radiation they work with.

Ultraviolet:

Ultraviolet radiation is emitted by the Sun and are the reason skin tans and burns. "Hot" objects in space emit UV radiation as well.

Radio:

Your radio captures radio waves emitted by radio stations, bringing your favorite tunes. Radio waves are also emitted by stars and gases in space.

electromagnetic spectrum

a bunch of types of radiation, organized by the amounts of energy they carry.

Electromagnetic radiation can be described in terms of

a stream of mass-less particles, called photons, each traveling in a wave-like pattern at the speed of light. Each photon contains a certain amount of energy. The different types of radiation are defined by the the amount of energy found in the photons.

Radiation is

any movement of energy through space or a wave made up of moving electrical and magnetic fields or a stream of particles called photons.

All EM radiation moves through the universe

at a constant speed of 300,000 km per second. It can even travel through the empty vacuum of outer space.

EM waves have

crests and troughs (wavelength = distance between crests).

Frequency is measured in

cycles per second, or Hertz.

An electric light, a microwave oven, a television set, an X-ray machine, a cell phone ... all of these machines use

electromagnetic energy.

Energy is measured in

electron volts.

Everything around us

emits, reflects, and absorbs EM radiation differently based on its composition.

Radiation is

energy that travels and spreads out as it goes - the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation.

Electromagnetic radiation can be expressed in terms of

energy, wavelength, or frequency.

Name two things that produce infrared rays. _____________________________ _______________________________

fires (radiation) (heat) ice (any object with temperature)

Which has a higher frequency: UV rays or gamma rays? ______________________

gamma rays

Sometimes an electron drops from one energy level to another,

giving off energy in the form of electromagnetic radiation.

Einstein showed that it is impossible for any object that has mass to

go faster than light.

It is possible for electromagnetic radiation to

go so fast, because it has no mass.

Which has the shorter wavelength: green light or red light? ____________________

green light

TV uses

high energy waves.

What are two ways that electromagnetic waves can be different from each other? i. ____________________________________________________________________ ii. ____________________________________________________________________

i. some have large wavelengths, others have small wavelengths ..... ii. long waves can carry TV signals (radio waves) but short waves can carry / give skin cancer, medium waves can be seen: "light waves" ..... Some EM waves have large wavelengths, others have small wavelengths. Therefore, various EM waves carry different amounts of energy.

What are two things that all electromagnetic waves have in common? i. ____________________________________________________________________ ii. ____________________________________________________________________

i. they can travel without a medium ..... ii. they all travel at the same speed (fastest speed in the universe) .....

Adding energy

increases the frequency of the wave, making the wavelength shorter.

Remote controls use

infrared rays to send signals to the TV set, stereo, DVD player.

What kind of rays are detected in a thermogram? ____________________________

infrared waves

Radio waves have photons with

low energies, microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and, the most energetic of all, gamma-rays.

AM radio uses

low energy waves.

So if you have a spaceship that you want to go really fast, you push it really hard. However by the time it is going nearly as fast as light, all your pushing is just

making it heavier, not faster. And the heavier it is, the harder it is to push!

FM radio uses

medium energy waves.

While some EM wavelengths are very long and measured in

meters, many are tiny and are measured in billionths of a meter: nanometers.

Wavelength is measured in

meters.

microwaves are used in

microwave ovens and airplane radar systems.

Which has the higher frequency: microwaves or television signals (radio waves)? ___________________________________

microwaves

The other types of EM radiation that make up the electromagnetic spectrum are

microwaves, infrared light, ultraviolet light, X-rays and gamma-rays.

However at high speeds (like a spaceship),

more of the push goes into changing the mass, and less goes into changing the speed.

UV rays occur

naturally in sunlight. The ozone layer blocks most UV radiation from reaching the surface of the Earth, fortunately. Can cause skin cancer and cataracts.

X rays have a high

penetrating power, they can travel easily through anything basically. takes photos of bones and organs. travel more easily through flesh than bone.

Visible light, due to special cells called cones, our eyes can

perceive wavelengths of visible light as color.

What does Radar stand for? _____________________________________________

radio detecting and ranging

Which has the longer wavelength: radio waves or x rays? _____________________

radio waves

Long EM waves such as

radio waves have the lowest frequency (highest wavelength) and carry less energy.

____________________________________________________ all depend on waves within the electromagnetic spectrum.

radio, remote, text, tv, microwave, x-rays at the doctor's office.

The electromagnetic (EM) spectrum is the

range of all types of EM radiation.

Lowest to highest color energy:

red, orange, yellow, green, blue, indigo, violet

With radar, microwaves are

reflected off an airplane and sent back to the radar system to pinpoint the exact location of the plane.

Gamma rays are the

shortest wavelength, highest frequency, highest energy waves in the Spectrum.

Electromagnetic Waves (EM Waves) are

similar to ocean waves: both are energy waves. They transmit energy.

Very short ones can give you

skin cancer.

Some of them are spread out (long wavelength), and some are

squashed together (small wavelength).

Infrared radiation can also be used to

take special photographs called thermographs.

The full range of wavelengths (shown below) is called

the electromagnetic spectrum. The wavelengths given are only approximate.

The faster something is going,

the more its mass is affected by pushing, and the less its speed is affected by pushing.

The higher the energy of the wave,

the more stuff it tends to pass through.

gamma rays are

the most energetic waves in the EM Spectrum. most of them coming from space are absorbed by our atmosphere but they are also produced on earth (high energy reactions, nuclear explosions). they do a lot of damage to living cells.

Frequency...

the number of these crests that pass a given point within one second.

Unlike ocean waves that require water, EM waves travel through

the vacuum of space at the constant speed of light.

In the oven, microwaves heat up

the water molecules in your food.

What part of your food absorbs the radiation in your microwave oven? ________________________________________________________________________

the water molecules within the food absorb the radiation in the microwave oven to heat the food up.

Electromagnetic Radiation and the Electromagnetic Spectrum (EMS)...

these waves spread across a spectrum from very short gamma rays to x-rays, ultraviolet rays, visible light waves, longer infrared waves, microwaves, to radio waves (can be longer than a mountain range).

radio waves are used to

transmit radio and television signals. (phones use it, stars emit it).....

The wavelengths of ultraviolet, X-ray, and gamma-ray regions of the EM spectrum are

very small. Instead of using wavelengths, astronomers that study these portions of the EM spectrum usually refer to these photons by their energies, measured in electron volts (eV). Ultraviolet radiation falls in the range from a few electron volts to about 100 eV. X-ray photons have energies in the range 100 eV to 100,000 eV (or 100 keV). Gamma-rays then are all the photons with energies greater than 100 keV.

EM Waves are produced by the

vibration of charged particles and have electrical and magnetic properties.

What is the lowest-frequency electromagnetic wave that our eyes can detect?___________________________________

visible light

We can only see

visible light.

Sometimes EM radiation behaves like a _________, other times it behaves like _____.

wave particles

Infrared and optical astronomers generally use

wavelength. Infrared astronomers use microns (millionths of a meter) for wavelengths, so their part of the EM spectrum falls in the range of 1 to 100 microns. Optical astronomers use both angstroms (0.00000001 cm, or 10-8 cm) and nanometers (0.0000001 cm, or 10-7 cm).

Astronomers who study radio waves tend to use

wavelengths or frequencies. Most of the radio part of the EM spectrum falls in the range from about 1 cm to 1 km, which is 30 gigahertz (GHz) to 300 kilohertz (kHz) in frequencies. The radio is a very broad part of the EM spectrum.

Electromagnetic energy can be thought of as

waves of pure energy that can travel without any medium. The waves all travel at the same speed, and they are the fastest things in the universe.

Infrared rays are often produced

when an object radiates heat. You can't see them but you do feel them.

Which has the lower frequency: yellow light or blue light? _____________________

yellow light

One reason is that when you push something,

you make it heavier as well as faster. At slow speeds (like cars and jet planes), the effect on mass is too tiny to notice: almost the whole push goes into changing the speed.