What types of waves are electromagnetic waves?
ELECTROMAGNETIC WAVES Transverse waves consisting of changing electric fields and changing magnetic fields Carry energy from place to place
HOW ARE THEY PRODUCED? Produced by constantly changing fields Electric Field A region of space that exerts electrical forces on charged particles Magnetic Field A region of space that produces magnetic forces Produced 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 fields They regenerate each other! Electromagnetic Radiation The transfer of energy by electromagnetic waves traveling through matter or across space
HOW THEY TRAVEL? Do NOT require a medium to transport energy Can travel through a vacuum, or empty space, OR through matter
CHECK POINT On 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 Michelson’s Experiment Activity
SPEED OF LIGHT In a vacuum (empty space) 3.0 x 10 8 meters per second
ELECTROMAGNETIC WAVES Differ in wavelength and frequency What is the relationship between wavelength and frequency? Electromagnetic radiation behaves sometimes like a wave, and sometimes like a particle
LIKE A WAVE? Young’s Experiment Page 536 (Superposition of waves)
LIKE A PARTICLE? Photoelectric Effect The emission of electrons from a metal caused by a light striking the metal Einstein proposed that light travels in packets of energy called PHOTONS The amount of energy that a photon has is proportional to the frequency of the electromagnetic wave Greater frequency = more energy
LIGHT WAVE INTENSITY Similar to sound intensity Light intensity is the same thing as brightness Photons of light travel outward from a light source in all directions The farther away from a light source an observer is, the less intense the light will be because it is spread out over a larger area
BEAD ACTIVITY Figure out what they do/ don’t 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 Activity
FLASHLIGHT ACTIVITY Inrto to visible light activity
WHITE LIGHT Made up of all the colors of the visible spectrum (ROY G BIV) Prisms As 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 COLOR Objects 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 colors
PRIMARY COLORS OF LIGHT Red, Green & Blue When colors of light are mixed together, the colors add together to form a new color
WHAT IS A PIGMENT A material that absorbs some colors of light and reflects others Primary Colors of Pigment Cyan, Magenta, & Yellow Used in printers – can be combined to make any color!
SEEING LIGHT The 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 materials
TYPES OF MATERIALS Transparent Transmits light A material that allows light to pass through it Translucent A material that scatters light Objects viewed through this type of material do not look distinct Opaque A material that either absorbs or reflects all of the light that hits it Does not allow any light to pass through
REFLECTION Why can you see yourself in a mirror? Aluminum foil demonstration Flat Crumpled
REFLECTION Regular Reflection Diffuse Reflection Parallel light waves strike a surface and reflect in the same direction Light hits a smooth, polished surface, like a mirror Parallel light waves strike a rough, uneven surface and reflect in many different directions
LAW OF REFLECTION Assumes light travels in straight lines When light strikes a surface it bounces off and can change directions Law of Reflection The angle of reflection is equal to the angle of incidence
TYPES OF MIRRORS Plane Mirror with a flat surface Produces a virtual image, or an exact copy of an object Convex The outside surface of a curved mirror is reflecting light Cause light rays to spread out Image is always upright and smaller than the actual object Concave The inside surface of a curved mirror is reflecting light Cause light rays to converge at a single point Uses: Vehicle headlights, produce a single bright beam of light
SCATTERING Light is redirected as it passes through a medium The atmosphere contains molecules and small particles that scatter sunlight Scattering causes deep red/ orange/ pink sunsets Particles 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 particles The light that remains for your eyes to perceive is made up of red and orange wavelengths
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 QUESTION What is the difference between reflection and refraction of light? Respond in sentence or bullet points
WHAT 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 LENSES ConcaveConvex Curved inward at the center Cause light rays to spread out Curved outward at the center Cause light rays to come together at one point (called a focal point)
FINDING YOUR BLIND SPOT Take 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.