Lenses and Mirrors Mrs. Gergel

Refraction of light 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 Mirage Rainbows

Index of refraction Light slows down as it passes mediums It travels fastest in air and slowest through glass Glass causes light to bend more than either air or water because glass refracts light more Index or refraction- a measure of how much a ray of light bends when it enters new material The higher the index refraction of a medium the more it bends light

Index of Refraction

Prisms and Rainbows When white light enters a prism each wavelength is refracted by a different amount When white light from the sun shines through tiny drops of water, a rainbow may appear Raindrops act like tiny prisms, refracting and reflecting light and separating colors Colors of the rainbow always appear in the same order because raindrops refract the shorter wavelengths the most

Mirages A mirage is an image of a distant object caused by refraction of light

Mirage Video

Lenses Lens is a curved piece of glass or other transparent material that is used to refract light A lens forms an image by refracting light rays that pass through it Lenses have different shapes Convex Concave The type of image formed by a lens depends on the shape of the lens

Concave Lenses A concave lens is thinner in the center than at the edges As parallel rays of light pass through a concave lens, they are bent away from the center of the lens Because the light rays never meet, a concave lens can produce only a virtual image

Virtual Image Virtual image- are right side up, or upright We see virtual images because brain assumes that light travels in a straight line. The brain treats the light rays as though they were coming from behind the mirror instead of being reflected

Convex Lenses Convex lens is thicker in the center than at the edges As parallel light rays pass through a convex lens, they are bent toward the center of the lens Rays meet at the focal point of the lens and then continue on The curved the lens, the more it refracts light The type of image formed by a convex lens depends on the position of the object in relation to the focal point. It may be a virtual image or a real image.

Real Image If the object is farther away from the mirror/lens than the focal point, the reflected rays form a real image Real image is formed when rays actually meet at a point Real images are upside down or inverted A real image may be larger or smaller than the object

Activity!

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 An image is a copy of an object formed by reflected or refracted rays of light Mirrors can be flat or curved the shape of the surface determine how the image will look

Plane Mirrors Plane mirror- a flat mirror that produces an upright virtual image the same size as the object The image you see in a plane mirror is a virtual image Virtual image- are right side up, or upright We see virtual images because brain assumes that light travels in a straight line. The brain treats the light rays as though they were coming from behind the mirror instead of being reflected

Concave Mirror A mirror with a surface that curves inward like the inside of a bowl is a concave mirror Focal point is the point at which the rays meet Concave mirrors can form either virtual images or real images The type of image depends on the position of the object in relation to the focal point

Convex Mirror A mirror with a surface that curves outward is called a convex mirror The focal point of a convex mirror is the point from which the rays appear to come Since the rays do not actually meet, images formed by convex mirrors are always virtual

Activity!