Unit 7 Study Guide

Unit 7 Study GuideTerm Definition

AbsorptionAmplitude

Angle of incidence Angle of reflection

ChlorophyllCones

Concave LensConvex Lens

CorneaCrest

Electromagnetic Spectrum

Electromagnetic Wave

Frequency Lens Lens

Longitudinal WavesMechanical Waves

MediumParallelPeriod

PerpendicularPhotoreceptorsRadiant Energy

Reflection Refraction

RetinaRods

Surface WaveTransmissionTransparent

Transverse WavesTrough

Visible LightWave

wavelengthWhite light

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Lesson 1: Waves What is a wave?

Wave: a disturbance that transports _____________ from one location to another location; the source of all waves is a VIRBRATION

o _____________ waves – require a mediumo _____________ waves – do NOT require a medium

Movement of Energy: ALL waves carry energy

o Examples: sound waves, ocean waves, mechanical waves Energy can move in three ways:

o Motion – kinetic energy (remember Unit 4)o Thermal Energy (unit 6)o Waves (unit 7)

Waves and Energy: Medium: the substance that the wave travels through Do ALL waves require a medium in order to travel?

o __________________________________________________________________.

Mechanical Waves: Mechanical Waves: waves the require a medium through which to travel

o The energy in the wave causes the individual particles in the medium to vibrateo As they vibrate, they “bump into” each other to transmit energy o The WAY in which they vibrate causes different types of waves

Two Types of Mechanical Waves: transverse and longitudinal waves _____________ Wave: waves in which the movement of the particles in the medium is perpendicular,

or at a right angle to the direction the wave is travelingo Example: Beach ball bouncing up and down

_____________ Wave: waves in which the movement of the particles in the medium is parallel to the direction the wave is traveling

o Example: sounds waves

Surface Waves in Water: _____________ (water) waves: a wave that travels on the surface of the water in both transverse and

longitudinal motions o Water particles travel in TWO directions, resulting in a circular motion

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Properties of Waves:Parts of a Wave:

Rest Position: where the medium lies when no wave is traveling through it

Crest: the _____________ point of the wave Trough: the _____________ point of the wave Amplitude: the height of a wave ____________: the distance from one point to another Period: the amount of time between one wave crest

and the next as it passes a specific location Frequency: the measure of how many wavelengths

pass a specific point per secondo Measured as “cycles per second” or _________

High and Low Frequency Waves: As frequency increases (waves per second), the wavelength decreases As frequency decreases (waves per second), the wavelength increases

Lesson 2: Electromagnetic WavesWhat are Electromagnetic Waves?

Electromagnetic Waves: waves of energy traveling through space

Mechanical & Electromagnetic Waves: Similarities: both have amplitude, wavelength and frequency Differences:

o Mechanical waves only transfer energy through a medium Speed depends on how dense the matter is that it is traveling through

o Electromagnetic waves DO NOT needs a medium (they can transfer energy in empty space (vacuum). Example - light traveling to Earth through the vacuum in space

Speed is FASTESTS through a vacuum then slows down as it travels through matter

Speed of Light “c” How fast is light? 300,000 km/s (in a vacuum) Can anything travel faster than light? No!

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Can you slow light down? No! Why do we see lightning flash before we hear thunder?

________________________________________________________________________________________________________________________________________________________________________

The Electromagnetic (or “EM”) Spectrum

Radio, Microwave, Infrared, Visible Light, Ultraviolet, X-ray, Gamma

Radiant Energy: the energy transmitted by an electromagnetic wave Electromagnetic Spectrum: the entire range of electromagnetic radiation, from the longest wavelength

to the shortest wavelength _____________ Light: the small section of the electromagnetic spectrum that human eyes can detect

Light from the Sun The Sun radiates many wavelengths of light to us, but the THREE main categories are:

o Infrared Light – carries the least energy o Visible Light – human eyes can detecto Ultraviolet Light – caries the most energy

Visible Light: Human eyes can only see the visible light portion of the EM Spectrum. Visible light consists of SEVEN ranges of wavelength, which our eyes perceive as color. “ROY G BIV”

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

Lesson 3: Light Waves

Light Waves and Matter – Transmission When light waves contact matter – there are THREE possible results:

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o _____________: the passing of light through an object or medium Examples: screens, glass, air, water

o Reflection: process whereby light _____________ from an object at the same angle of intensity that the object received it

Examples: Mirror, colored objects, windows

o Absorption: the ability of light waves to be taken into an object or medium, rather than transmitted (passed through) or reflected (bounced off).

Examples: black objects absorb all colors, colored objects absorb all colors except the one we see (which is the one reflected)

White Light White Light: contains all the colors of the visible spectrum

How We See Colors Why does an apple appear red?

o An apple looks red because the apple absorbs all the colors of light, EXCEPT for the color red which is reflected back to your eyes.

What is color?o The color we see is determined by the wavelength of the light reflected from an object.

How Eyes Detect Light How do our eyes process wavelengths to see “color?”

o Our eyes have a special area for detecting light called the RETINA.

Retina: the layer of cells at the back of the eye where light-sensitive cells are found. Photoreceptors: cells on the retina that detect different wavelengths of light and send these signals to

the brain

Two Types Photoreceptors of the Retina Cones: special light-sensitive cells in the retina that allow us to see colors and fine details Rods: cells in the retina that are sensitive to all light but do not distinguish color

How Plant Cells Interact with Light Why are plant leaves (almost always) green?

o Plants respond to light too! They have chemical called chlorophyll that absorbs mostly red and blue wavelengths of light, but reflects the wavelength for the color green.

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Lesson 6: Reflection and RefractionRemember!

Reflection: process whereby light bounces from an object at the same angle and intensity that the object received it.

Refraction: the change in direction of light when it goes from one medium to another medium. Medium: a substance or material in which something exists or occurs.

Light Rays When light travels through a uniform medium, (example air), it DOES NOT change direction. Transmission: when light passes through an object, such as a window Absorption: when light strikes an object, such as a wall, and is not transmitted or reflected

Reflection, Transmission, and Absorption What are the basics of how light moves?

o Typically, light is NOT solely reflected, or transmitted, or absorbed. Instead, it often does all THREE to a varying degree.

How Reflection Works Law of Reflection: Angle of Reflection = Angle of Incidence

Angle of _____________: the angle that a light ray makes with the line normal (or perpendicular) to the surface.

Angle of _____________: the angle the ray bouncing off the mirror makes with the same normal line.

How REFRACTION Works How does a straw in a glass of water look bent from some angles, even though it is really straight?

o Light has different SPEEDS in different materials. o When light moves from one transparent medium to another, it often changes speed. o The change in speed causes the light to change direction, and this change of direction is called

_____________.

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Refraction: From Air to Water What happens to light when it travels from AIR to WATER?

o When light enters water, it slows down, causing the light ray to bend.

o The refracted ray bends at an angle SMALLER than the angle of the ray entering the water (angle of incidence)

Refraction: From Water to Air What happens to light when it travels from water to air?

o When light goes from the water to the air, it speeds up, so it bends in the OPPOSITE direction, away from the normal line.

Rainbows What happens to white light, such as sunlight, that causes it to

form a rainbow?o Rainbows in the sky occur when sunlight refracts through

droplets of water. o Each color has a different range of wavelength and therefore bends by a slightly different

amount.

Light is Everywhere! Look at the picture of the glass on the porch light; how much light is

reflected, absorbed, and transmitted by the glass?o Glass transmits a lot, reflects some, and absorbs very little

Lesson 7: LensesRemember!

Retina: layer of cells at the back of the eye where light sensitive cells are found.

How do we see? How do we see everyday objects around us?

o Light is reflected of them and into our eyes, and is detected by light sensitive cells in your retina.

Lens: a transparent object with at least one curved surface.

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o The greater the curve of the lens, the more the light will bend as it passes through it. Transparent: able to let light pass through.

Concave Lens: these are thicker at the _____________ than in the middle; curve inward.

o ConCAVE = caved in. o Cause the light rays passing through them to spread apart.

Convex Lens: are thicker in the _____________ than at the edge; curve outward. o They cause the light rays passing through them to come together.

Concave Lens: How does looking through a concave lens change the shape of the object?

o Makes it appear SMALLER than it actually is

Convex Lens: How does looking through a convex lens change the shape of the object?

o Make is appear LARGER than it really is

The Human Eye Cornea: the transparent part of the eye that covers the pupil and the

iris. How does the cornea and lens work together to help us see?

o When light rays reflected off an object pass into the eye, the CORNEA and then the lens BEND the light rays toward each other.

o The light rays come together and strike the light-sensitive cells in the retina at a single spot. These cells then send SIGNALS to the brain.

o The brain interprets these signals as an IMAGE.

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