The Electromagnetic Spectrum & Light

The Electromagnetic Spectrum & LightChapter 18What types of waves are electromagnetic waves?Electromagnetic WAvesTransverse waves consisting of changing electric fields and changing magnetic fields

Carry energy from place to placeHow are they produced?Produced by constantly changing fields

Electric FieldA region of space that exerts electrical forces on charged particles

Magnetic FieldA region of space that produces magnetic forcesProduced by magnets, by changing electric fields, and by vibrating charges

How they Travel?Changing electric fields produce changing magnetic fields and changing magnetic fields produce changing electric fieldsThey regenerate each other!

Electromagnetic Radiation The transfer of energy by electromagnetic waves traveling through matter or across spaceHow they Travel?Do NOT require a medium to transport energy

Can travel through a vacuum, or empty space, OR through matterCheck PointOn your white board, answer the following question:

Compared to the direction of wave movement, in what direction do the magnetic and electric fields of an electromagnetic wave vibrate?How fast is Light?Thunder & Lightning example

Michelsons Experiment ActivitySpeed of light In a vacuum (empty space)3.0 x 108 meters per secondElectromagnetic WavesDiffer in wavelength and frequencyWhat is the relationship between wavelength and frequency?

Electromagnetic radiation behaves sometimes like a wave, and sometimes like a particleLike a wave?Youngs ExperimentPage 536 (Superposition of waves)

Like a Particle?Photoelectric EffectThe emission of electrons from a metal caused by a light striking the metal

Einstein proposed that light travels in packets of energy called PHOTONSThe amount of energy that a photon has is proportional to the frequency of the electromagnetic waveGreater frequency = more energy

Light Wave IntensitySimilar to sound intensityLight intensity is the same thing as brightnessPhotons of light travel outward from a light source in all directionsThe farther away from a light source an observer is, the less intense the light will be because it is spread out over a larger areaElectromagnetic Spectrum ProjectPowerPoint ProjectBead ActivityFigure out what they do/ dont do, put them in order, take a phone picture, send an e-mail to Ms. Williams with your pic along with a description of what the beads do and why you think they do it!Page 544 Sunscreen ActivityFlashlight activityInrto to visible light activityBehavior of Light18.3Warm-UpList the parts of the electromagnetic spectrum in order of longest wavelength to shortest wavelength

Light behaves both like a wave and like a ______________.

ColorWhite lightMade up of all the colors of the visible spectrum (ROY G BIV)

PrismsAs white light passes through a prism, shorter wavelengths refract more than longer wavelengths, and the colors separate (called dispersion)Red bends the least (top of rainbow)Violet bends the most (bottom of rainbow)

Seeing ColorObjects appear to be a certain color because they are reflecting that color of light and absorbing all the other colors

A red shirt reflects red light and absorbs all the other colorsPrimary Colors of LightRed, Green & Blue

When colors of light are mixed together, the colors add together to form a new colorWhat is a pigmentA material that absorbs some colors of light and reflects others

Primary Colors of PigmentCyan, Magenta, & YellowUsed in printers can be combined to make any color!Seeing LightThe reason we are able to see objects is because light bounces off those objects, through matter, and then into our eyes

Light is not able to pass through all materialsTypes of MaterialsReflectionWhy can you see yourself in a mirror?

Aluminum foil demonstrationFlatCrumpledReflectionRegular ReflectionDiffuse ReflectionParallel light waves strike a surface and reflect in the same directionLight hits a smooth, polished surface, like a mirrorParallel light waves strike a rough, uneven surface and reflect in many different directionsLaw of ReflectionAssumes light travels in straight lines

When light strikes a surface it bounces off and can change directions

Law of ReflectionThe angle of reflection is equal to the angle of incidence

Types of Mirrors

RefractionA light wave bends (or refracts) when it passes at an angle from one medium into another

Causes MiragesA false or distorted image (p 548)

ScatteringLight is redirected as it passes through a medium

The atmosphere contains molecules and small particles that scatter sunlight

Scattering causes deep red/ orange/ pink sunsetsParticles in the atmosphere cause the shorter wavelengths of visible light to scatter (like blue and green)At sunrise and sunset light travels a greater distance to get to your eyes so it runs in to more particlesThe light that remains for your eyes to perceive is made up of red and orange wavelengths

Why is the sky blue?Scattering!When the sun is high in the sky it travels a shorter distance to the observer

Particles and molecules in the atmosphere scatter blue light in all directions more so than any other color of light, so the sky appears blue

Air is COLORLESS!EXIT QuestionWhat is the difference between reflection and refraction of light?Respond in sentence or bullet pointsWhat is a lens?An object made of transparent material that has one or two curved surfaces

Lenses refract (or bend light)Depends on lens curvature and thickness

Types of lensesConcaveConvexCurved inward at the center

Cause light rays to spread outCurved outward at the center

Cause light rays to come together at one point (called a focal point)

The EyeFigure 17

NearsightednessFigure 18

NearsightednessFigure 18

FarsightednessFigure 19

FarsightednessFigure 19

Finding your blind spotTake an index card, make an X on the card about 3-4 cm from the right hand edge. Next draw a dot 5-6 cm to the left of the X.

Cover your right eye, stare at the X with your left eye. Slowly move the card closer to your eye until the dot disappears. Have your partner use a meter stick to measure the distance from your eye to the index card.