Section 1: Waves and the Electromagnetic Spectrum What causes waves? What are the basic properties of waves? What does an electromagnetic wave consist of? What are the waves of the electromagnetic spectrum?

Electromagnetic Waves Believe it or not, you are being “showered” all the time, not by rain but by waves.

Transverse Waves Waves that move the medium perpendicular to the direction in which the waves travel are called transverse waves.

Properties of a Wave Amplitude: The maximum distance that the medium carrying the wave energy moves away from the resting position.

Properties of a Wave Wavelength: The distance between two similar parts of a wave.

Properties of a Wave Frequency: The number of times a wave passes an area in 1 second. Measured in Hertz (Hz).

Properties of a Wave Speed: How fast a wave travels. Measured in kilometers per second (km/s). Mechanical Waves: The speed can change depending on the medium and the energy. Can be slow or fast, but they can NEVER be as fast as electromagnetic waves. Electromagnetic Waves: Always travel at “the speed of light” (300,000 km per second in a vacuum). They will slow down a bit when going through mediums like air or glass.

Amplitude, Wavelength, and Frequency The basic properties of all waves are amplitude, wavelength, and frequency.

Mechanical Waves Mechanical waves are produced when a source of energy passes through a medium. Examples: Sound Earthquakes Ocean waves “Snapping” a rope

What Is an Electromagnetic Wave? An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light. They do NOT require a medium to travel.

What Is the Electromagnetic Spectrum? The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency.

Radio Waves Longest wavelength (and lowest frequency) Uses the least amount of energy (and is therefore the safest of all E.M. waves) Used to broadcast FM and AM radio signals Was once used to broadcast television signals CB Radio (popular with truck drivers)

Microwaves Used to heat up food in microwave ovens Also used for cell phone communication

Infrared Rays Usually in the form of invisible heat (stove, fire, etc.) Can also be used for night vision and thermography

Makes up a very small part of the very large Electromagnetic Spectrum Visible Light Makes up a very small part of the very large Electromagnetic Spectrum

Visible Light The human eye can only see wavelengths between 800 nanometers (red light) to 400 nanometers (violet light). 1 billion nanometers = 1 meter (about 3 feet)

Visible Light The main colors of visible light (in order of largest to smallest wavelength): ROY G BIV

Visible Light “White light” is actually all the colors of the visible spectrum blended into one. Light is separated into the colors of the visible spectrum when it passes through a prism.

Ultraviolet (U.V.) Rays Small amounts are useful to humans (skin can convert UV rays into Vitamin D). Buy sunblock that has the highest UVA and UVB protection (the best sunblocks contain zinc oxide). Large amounts are harmful to humans (leading cause of skin cancer).

X-Rays Can pass through most objects except dense matter (like bone or lead). Excessive exposure can lead to cancer, but getting 3 - 4 X-ray exams a year is considered safe.

Gamma Rays Shortest wavelength (and highest frequency). Most dangerous of all electromagnetic waves. In small, concentrated doses, can be used to kill cancer cells.

End of Section: Waves and the Electromagnetic Spectrum

Section 2: Visible Light and Color How does visible light interact with an object? What determines the color of an opaque object? How is mixing pigments different from mixing colors of light?

When Light Strikes an Object When light strikes an object, the light can be reflected, transmitted, or absorbed. Key Term Transmit : to send from one place to another

Visible Light Transparent: material that allows light to transmit through it in straight lines examples: clear glass, clean air Translucent: material that scatters transmitted light as it passes through it examples: fog, frosted glass Opaque: material that reflects some colors and absorbs other colors; does not allow any light to pass through examples: walls, mirrors

The Color of Objects The color of an opaque object is the color of the light it reflects.

Combining Colors : Light . When combined in equal amounts, the three primary colors of light (green, red, and blue) produce white light. The primary colors can also form other colors (example: red and green make yellow).

Combining Colors : Pigments Pigments are found in inks, paints, and dyes. They absorb some colors while they reflect others. The primary colors of pigments (magenta, yellow, and cyan) combine in equal amounts to form black.

End of Section: Visible Light and Color

Section 3: Reflection and Refraction What does the law of reflection state? Why do light rays bend when they enter a new medium at an angle? What determines the types of images formed by convex and concave lenses?

The Law Of Reflection When an object or wave hits a surface through which it cannot pass, it reflects (bounces back).

Concave Mirrors A mirror with a surface that curves inward like the inside of a bowl is a concave mirror.

Concave Lenses A concave lens will make a larger real object look like a smaller “virtual” image.

Examples of Concave Mirrors & Lenses Make-Up Mirrors Glasses for Nearsightedness

Convex Lenses How can you make this tiny ladybug appear larger? A convex lens will make a small real object look like a larger “virtual” image.

Examples of Convex Mirrors & Lenses Blind-spot Mirrors Magnifying Lens Reading Glasses

Refraction of Light When light rays enter a medium at an angle, the change in speed causes the rays to bend, or change direction.

The Index of Refraction The index of refraction of a medium is a measure of how much light bends as it travels from air into the medium. The table shows the index of refraction of some common mediums.

The Index of Refraction Interpreting Data: Which medium causes the greatest change in the direction of a light ray? Diamond causes the greatest change in the direction of a light ray traveling from air.

The Index of Refraction Interpreting Data: According to the table, which tends to bend light more: solids or liquids? According to the graph, most solids bend light more than liquids do (quartz is an exception).

The Index of Refraction Predicting: Would you expect light to bend if it entered corn oil at an angle after traveling through glycerol? Explain. You would not expect light to bend if it entered corn oil at an angle after traveling through glycerol, because corn oil and glycerol have the same value for the index of refraction.

End of Section: Reflection and Refraction

Section 4: Seeing Light How do you see objects? What types of lenses are used to correct vision problems?

Cross-Section of the Eye ___________________ : Hole through which light enters the eye. Transparent front surface of the eye. Short, thick nerve through which signals travel to the brain from the eye.

Cross-Section of the Eye ___________________ : Ring of muscle around the pupil. ___________________ : Curved part of the eye behind the pupil that refracts light. ___________________ : Layer of cells lining the inside of the eyeball.

Pupil and Iris The iris (the colored part of the eye) is a ring of muscle that opens and closes depending on how much light needs to enter the eye. The pupil (black hole) is simply the opening made by the iris.

Retina The retina is a layer of cells that lines the inside of the eyeball. Contains two types of cells: Rods able to see with very little light can only see black and white images Cones respond to colors red, green, and blue needs bright light to function properly

Correcting Vision Concave lenses are used to correct nearsightedness. Convex lenses are used to correct farsightedness.

End of Section: Seeing Light

Section 5: Optical Tools How are lenses used in cameras, telescopes, and microscopes?

reorder slides Cameras The lens of the camera focuses light to form a real, upside-down image on film in the back of the camera.

Microscopes A microscope uses a combination of lenses to form enlarged images of a tiny object.

Telescopes Telescopes use lenses or mirrors to collect and focus light from distant objects.

End of Section: Optical Tools