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Light

Light. Electromagnetic Radiation. Electromagnetic waves (E.M.) are transverse waves produced by the motion of electrically charged particles ( photons ).

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Light

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  1. Light

  2. Electromagnetic Radiation • Electromagnetic waves (E.M.) are transverse waves produced by the motion of electrically charged particles (photons). • E.M. waves do not require a medium, and are therefore able to travel at 186,000 mi/s (300,000 km/s), the speed of light (which is an E.M. wave).

  3. Electromagnetic Spectrum • The different electromagnetic waves are arranged in the electromagnetic spectrum in order of increasing frequency and decreasing wavelength. • The higher the frequency, the more photons (energy) per wave, and the more potentially harmful the wave is.

  4. Low energy High energy

  5. Radio Waves • Radio waves are the lowest frequency E.M. wave. • They are used primarily for communications, such as cell phones, t.v. and radio transmissions, and cordless devices such as phones, speakers, etc.

  6. Microwaves • Microwaves are a type of radio wave. They are used in cell phones and microwave ovens. • At normal levels, microwaves are harmless.

  7. Infrared Radiation • Infrared radiation transfers energy in the form of heat. • Examples include heat lamps and the warmth from the sun. Special types of film and cameras can show infrared radiation. This is called thermography.

  8. Ultraviolet Light (U.V.) • U.V. rays are potentially dangerous at high levels or with prolonged exposure. • U.V. rays can cause sunburns and skin cancer, and kill bacteria and healthy cells.

  9. The ozone layer of the atmosphere blocks most u.v. rays from reaching the earth. • Using sunscreens with high S.P.F. ratings can also help protect your skin from u.v. rays.

  10. X-Rays • X-rays are high frequency e.m. waves which are potentially dangerous at moderate levels. • X-rays can penetrate many materials such as skin, muscle, and many fabrics.

  11. Visible Light • Visible light can be separated into 7 different colors. From lowest frequency to highest, they follow the acronym ROY G. BIV • When all 7 colors are combined together they produce white light.

  12. Prisms & Rainbows • Prisms: Separates white light into its component colors. • The longer the wavelength, the less it will be bent by the prism. • Rainbows- light shining thru tiny droplets of water, each droplet acts as a prism

  13. Color • The color of the object you see is the light that is reflected from its surface. All other colors are absorbed by the object.

  14. Primary & Secondary Light Colors • The 3 colors of light that can combine to form all other colors are primary colors – • a. Red, Blue, Green • i. Equal Red + Equal Blue = Magenta (secondary color) • ii. Equal Red + Equal Green = Yellow (secondary color) • iii. Equal Green + Equal Blue = Cyan (secondary color) • iv. Equal Red + Equal Green + Equal Blue = White Yellow Magenta Cyan

  15. Pigments • Pigment– substance that color other materials like paints, inks, etc • a. Primary Pigments are Cyan, Yellow & Magenta • b. Cyan + Yellow + Magenta = Black • c. Cyan + Yellow = Red • d. Yellow + Magenta = Red • e. Cyan + Magenta = Blue • f. The primary pigments are the secondary light colors! Red Blue Green

  16. Compare Lights & Pigments • Three primary colors = three secondary pigments • Three primary pigments = Three secondary colors

  17. Transparent materials allow almost all visible light to pass through. Ex.: glass, plastic wrap

  18. Translucent materials allow a partial amount of visible light to pass through. Ex.: wax paper, shower doors, plastic milk jugs

  19. Opaque materials stop almost all visible light from passing through. Ex.: drywall, thick curtains

  20. Reflection & Mirrors • When light strikes an object • It is either reflected, absorbed or transmitted. • Opaque: a material that reflects or absorbs the light – can’t see through it. -wood • Transparent: The material transmits light – allows light to pass through it– glass • Translucent: allows some light to pass through – can’t see image clearly – wax paper, frosted glass.

  21. Kinds of Reflections • You see objects because light is reflected, bounced off of it. • Law of Reflection: Angle of incidence equals the angle of reflection– • Angle coming in = angle going off • Regular Reflection: reflection off smooth surface – a mirror • Diffuse Reflection: Irregular or bumpy, uneven surface – wall

  22. Refraction • Refractionof Light: Bendor change direction • 1. As light rays enter a new medium the cause light to bend • 2. The denser the medium – the slower the light travels • 3. Index of Refraction: a measure of how much a medium bends the light that travels through it. • 4. The faster the beam, it will bend away from normal, the slower the beam, it will bend toward the normal.

  23. 3 Types of Mirrors • Plane Mirror: a flat mirror – produces an image that is right side (virtual) up and the same size as the original object – • Concave Mirror: a mirror with a surface curved inward like a “cave” or a bowl. • Light reflected comes together to meet at a Focal Point. • Can produce virtual or real images • Convex Mirrors: • A mirror w/ a curved surface facing outward • Reflected rays appear to come from a focal point behind the mirror • Images formed are always Virtual Concave mirror Convex mirror Plane mirror

  24. Real or Virtual? • Image: a copy of an object formed by reflected or refracted light • Virtual image: right side up appears to be coming from behind the mirror. • Real Image: is formed when reflected light rays actually meet at a point. The image is upside down (inverted),

  25. Lens – Concave & Convex • Lenses – a curved piece of material used to bend light • Convex lenses: cause light passing through to bend toward the focal point. • (converging) • The images produced depends on the position of the object • Concave lenses: as light passes through, they are bent away from the center • (diverging) • Images produced are only virtual, not real Convex Lens Concave Lens

  26. Polarized Light • Normal light will produce waves which vibrate in many different planes. • Polarized light is light which vibrates in only 1 plane. This is created by passing normal light through a polarized lens.

  27. Polarized lenses block all light waves except those moving in 1 particular plane.

  28. Polarized glass and lenses are effective at blocking out glare from the sun. As a result they are used in car windshields, sunglasses, and camera lenses.

  29. A mirage is a visual distortion produced by the refraction of light. • Some mirages produce a mirror or a watery image, and others may make an object appear larger or smaller, nearer or further away.

  30. This device produces a false image, but not a true mirage.

  31. I cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg. The phaonmneal pweor of the hmuan mnid. Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh?

  32. Vision - Structure Need to know these structures & their function: • Ciliary muscle: ligaments attach the lens to these, they contract & stretch the lens allowing near & far focus • Vitreous humor: fluid inside eyeball maintains size & shape of the eye • Retina: contains the rods & cones that are sensitive to light • Choroid coat: middle layer of the eyeball • Sclera: the outer “whites of the eye” • Optic nerve: takes rod & cone impulse back to the occipital lobe for processing

  33. Image Processing • Fovea – The central region where images focused is the fovea. • Rods – about 1 billion, sensitive to brightness, light and dark & movement • Cones – detect color, about 3 million. 3 types of cones, sensitive to red, blue & green wavelengths of light. • All rods & cones have nerve fiber attached, these collect at the back of the eye and form the optic nerve which carries the signal back to the eye.

  34. Lasers & Coherent Light • Coherent light is visible light traveling at only 1 specific wavelength (resulting in 1 color). This wave has all of it’s crests and troughs aligned and travels in only 1 direction. A laser is an example of coherent light.

  35. A laser is a device used to create a beam of coherent light.

  36. Lasers • In a laser, an electric current excites a material (like neon) and causes it to emit photons. These photons are enclosed inside the laser device where they bounce back and forth between 2 mirrors and becomes perfectly aligned (coherent light).

  37. Some of these photons, if they are aligned correctly, escape through a small portion of one of the mirrors. This is the laser beam.

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