Waves, Sound, and Light

Chapter 3

Bell Work 11/29/10

Please get a new bell work sheet. Write each statement then decide if they are true or false, if false correct them.

1. Mechanical waves transfer energy through a vacuum.

2. A wave is a disturbance that transfers energy.

3. An example of a longitudinal wave is a water wave.

Light 3.1 Vocab

Electromagnetic wave – a disturbance that transfers energy through a field

Radiation – energy that moves in the form of EM waves

How EM waves form and sources of EM waves

• Electric and magnetic fields make up EM waves

• Many of the EM waves on Earth’s environment come from the Sun.

• Stars give off EM waves but since they are so far away not many of their waves hit the Earth

• Technology is also a source of EM waves

Bell Work 11/30/10

1. What are the two types of fields that make up an EM wave?

2. How are EM waves used to measure distances in space?

3. How does microwave cooking depend on reflection?

Electromagnetic spectrum

• The range of all EM frequencies• The spectrum goes from the lowest

frequencies to the highest frequencies• Higher-frequency EM waves with more

electromagnetic vibrations per second have more energy than lower-frequency EM waves

Measuring EM Waves

• EM wave frequency is measured in hertz (Hz)

• One hertz equals one cycle per second

Radio waves

• Have the longest wavelengths, the lowest frequencies, and the lowest energies

• Examples of radio waves are AM/FM radio and broadcast television

Microwaves• EM waves with shorter wavelengths, higher

frequencies, and higher energy than other radio waves

• Radar – radio detection and ranging. Used to control air traffic at airports, analyze weather conditions and measure the speed of a moving vehicle

• Radar led to the invention of microwave ovens

• Cell phones – radio transmitter and receiver that uses microwaves

Bell work 11/25/09

1. List the colors of the visible light spectrum in order from longest wavelength to shortest wavelength.

2. What are the 7 parts of the electromagnetic spectrum?

Bell Work 11/30/09

Please use complete sentences

1. Give an example of using a radio wave.

2. Give an example of using a microwave.

3. Give an example of using an x-ray.

Bell Work 12/1/09

1. What do electromagnetic waves transfer energy through?

2. What is radiation?

3. How does a microwave cook food?

Visible Light

• The part of the EM spectrum that human eyes can see.

• Longest wavelengths are red all the way to violet

• ROY G BIV

• Red, Orange, Yellow, Green, Blue, Indigo, Violet

Bell Work 12/2/09

1. What are EM waves measured in?

2. Give two examples of using a radio wave.

3. Give 3 examples of using a microwave.

4. List the colors of visible light from longest wavelength to shortest wavelength.

Infrared Light

• Type of EM wave most often associated with heat

• Sometimes referred to as heat rays

• You can feel it as warmth coming from the sun, a fire, or a radiator

• Infrared lamps are used to provide warmth in bathrooms and to keep food warm after its been cooked

• Some animals can see in infrared light

Ultraviolet Light• Has more energy than visible light• The waves in this range can damage your skin and

eyes• Sun block and UV-protection sunglasses are

designed to filter out the higher frequencies• UV light can be used to sterilize medical instruments

and food by killing harmful bacteria• IV light causes skin cells to produce vitamin D which

is essential to good health• UV light is visible to some animals. Bees and some

other insects

X-rays

• Has a very high frequency and energy

• Pass easily through soft tissues of the body, but are absorbed by the bone

• The x-rays pass through exposing the film where there is no bone

• When getting x-rays other parts of the body are covered with a lead vest to block the x-rays

http://www.casualtysimulation.com/gallery/d/551-2/broken_foot_x_ray

Gamma rays

• Highest frequencies and energies of any EM waves

• Produced by some radioactive substances as well as the sun and other stars

• Gamma rays can penetrate the soft and the hard tissues of the body, killing normal cells and causing cancer cells to develop

• Gamma rays can also be used to kill cancer cells and fight tumors

Bell Work 12/3/091. Which group from the EM spectrum has

the highest frequencies?

2. Which group pass easily through soft tissues of the body, but are absorbed by the bone?

3. What can you use to filter out the high frequencies of UV rays?

4. Which EM wave is most associated with heat?

Bell Work 12/4/09

Predict what would happen if you kept a green plant in the dark for one month. Explain why. (at least 3 sentences)

Vocab 3.3

Incandescence – the production of light by materials at high temperatures

Luminescence – the production of light without the high temperature. Many organisms produce their own visible light through this.

Bioluminescence – production of light by living organism. These organism produce light from chemical reactions rather than intense heat.

Fluorescence – occurs when a material absorbs EM radiation of one wavelength and gives off EM radiation of another.

Bell Work 12/5/09

1. What happens to the speed of EM waves in a vacuum?

2. What happens when microwaves encounter water?

3. What produces the most EM waves on Earth?

Light 3.4 Notes

Transmission – the passage of an EM wave through a medium.

• If the light reflected from objects did not pass through the air, windows, or most of the eye, we could not see the objects

Absorption – the disappearance of an EM wave into the medium

• Absorption affects how things look, because it limits the light available to be reflected or transmitted

How Materials Transmit Light

• Transparent materials allow most of the light that strikes them to pass through.

• Translucent materials transmit some light, but they also cause it to spread out in all directions.

• Opaque materials do not allow any light to pass through them, because they reflect light, absorb light, or both

Scattering – the spreading out of light rays in all directions, because particles reflect and absorb the light

• Fog or dust in the air, mud in water, and scratches or smudges on glass can all cause scattering

• Scattering creates a glare and makes it hard to see even through a transparent material

Polarization – a quality of light in which all of its waves vibrate in the same direction

• Polarizing filters reduce glare and make it easier to see objects

Prism – a tool that uses refraction to spread out the different wavelengths that make up white light

• Prisms split light into colors by refracting wavelengths in different amounts

Color Reflection and Absorption

The color of an object or material is determined by two factors

1. the wavelengths it absorbs and those it reflects

2. The wavelengths present in the light that shines on the object

• A material that reflects all wavelengths of visible light appears white

• A material that absorbs all wavelengths of visible like appears black

• A green lime absorbs most wavelengths but reflects green, so the lime looks green

Primary Colors of Light

• The human eye can detect only 3 color bands: red, green, and blue

• Your brain perceives these three colors and various mixtures of them as all the colors

Primary colors – red, green, and blue – can be mixed to produce all the possible colors

Primary Pigments

• Materials can be mixed to produce colors just as light can

• Materials that are used to produce colors are called pigments

Primary pigments – cyan, yellow, and magenta

Bell Work 12/8/09

1. What color is something that absorbs all the colors?

2. What color is something that reflects all colors?

3. If an object absorbs most wavelengths but reflects violet what color will it be?

Bell Work 12/9/09 – (fill in the blanks)

1. Bioluminescent animals produce light through _________.

2. When light is absorbed into a medium, the waves ________ in the medium.

3. The primary pigments create colors through _____________ mixing.

4. An electromagnetic wave transfers energy through a ______.

5. Most of the visible EM waves on Earth come from the ______.