Light Section 1 Light Hits an Object When light strikes an object, the light can be reflected, absorbed, or transmitted. Vocab Opaque-A material that reflects or absorbs all of the light that strikes it Transparent-a material that transmits light Translucent- a material that scatters light as it passes through Light A material that reflects or absorbs all of the light that strikes it is opaque. You cannot see through opaque objects. Examples of opaque materials include wood, metal, and cotton and wool fabrics. A transparent material transmits light. When light strikes a transparent object, it passes right through, allowing you to see what is on the other side. Clear glass, water, and air are examples of transparent materials Other materials allow some light to pass through. This type of material is translucent. Translucent materials scatter light as it passes through. You can usually tell that there is something behind a translucent object, but you cannot see details clearly. Frosted glass, and wax paper are translucent. Kinds of Reflection You can see most objects because light reflects, or bounces, off them. What you see when you loot at an object depends on how its surface reflects light. Vocab Ray-straight line used to represent a light ray Regular Reflection- reflection that occurs when parallel rays of light hit a smooth surface and all reflect at the same angle Regular Reflection To show how light travels and reflects, you can represent light waves as straight lines called rays. Light rays reflect from a surface according to the law of reflection: the angle of reflection equals the angle of incidence. Regular Reflection cont. Regular reflection occurs when parallel rays of light hit a smooth surface. All the rays are reflected at the same angle. Mirrors A mirror is a sheet of glass that has a smooth, silver-colored coating on one side. When light passes through the glass, the coating on the back reflects the light regularly, allowing you to see an image. Mirror Vocab Image-a copy of an object formed by reflected or refracted rays of light. Plane Mirror- a flat mirror that produces an upright, virtual image the same size as the object Virtual Image- an upright image formed where rays of light appear to meet or come from Vocab Cont. Concave Mirror- a mirror with a surface that curves inward Focal Point- the point at which rays of light meet or appear to meet after being reflected (or refracted) by a mirror (or lens) Real Image-An inverted image formed where rays of light meet Convex Mirror- a mirror with a surface that curves outward Plane Mirror The image is the same size as you (bathroom mirror) The image is the same distance away as you are Produces an image that is right-side up and the same size as the object being reflected Virtual Images The image you see when you look in a plane mirror is a virtual image. Virtual images are right-side up, or upright. Virtual describes something that you can see, but does not really exist. You cant reach behind a mirror and touch your image. Concave Mirror a concave mirror can reflect parallel rays of light so that they meet at a point. Concave mirrors can form either virtual images or real images. The type of image formed by a concave mirror depends on the position of the object in relation to the focal point. Convex Mirrors Some convex mirrors reflect parallel rays of light. The rays spread out but appear to come from a focal point behind the mirror. Since the rays do not actually meet, images formed by convex mirrors are always virtual. Convex Mirrors cont. Objects seen in the mirror are closer than they appear? Because a convex mirror spreads out rays of light, you can see a larger reflection area than you can with a plane mirror. Because you see more in the mirror, the images appear smaller and farther away than the objects themselves. Light Section 2 Refraction and Lenses Refraction of Light Think about a fish tank. What are the mediums the light has to go through? - water; glass; air When light rays enter a new medium at an angle, the change in speed causes them to bend, or change direction. Refraction can cause you to see something that may not actually be there. It can form a mirage, or cause a beautiful rainbow to appear. Index of Refraction Index of refraction- is a measure of how much a ray of light bends when it enters that material Some mediums cause light to bend more than others Light travels the fastest in air and empty space Glass Can cause light to bend more because glass refracts more- it has a higher index of refraction The higher the index of refraction, the more it bends light Prism White light is actually a mixture of many wavelengths of color When white light passes through a prism, the lights separate into the component colors Rainbows When white light from the sun shines through tiny drops of water, a rainbow may appear The colors of the rainbow always appear in the same order because of how the light refract the wavelengths Mirage A mirage is an image of a distant object caused by refraction of light A mirage is caused by rays being bent as they go from cooler air up high to warmer air near the Earths surface Lenses Lens A lens is a curved piece of glass or other transparent material that is used to refract light It forms an image by refracting light rays that pass through it Concave Lens Concave lens- a lens that is thinner in the center than at the edges Because the light rays never meet, a concave lens can only produce a virtual image Convex Lens Convex lens- a lens that is thicker in the center than at the edge The more curved the lens, the more it refracts light It acts somewhat like a concave mirror, because it focuses rays of light How does refraction work if I put a pencil in a cup of water?