Mirrors

Reflection Light always travels in a straight line However, when light hits another substance, it will change direction Is a material is opaque (not transparent or translucent; impenetrable to light; not allowing light to pass through.), the light will not pass through it but bounce off The change in the direction of light is called reflection.

Texture of the Surface The manner in which the light reflects depends on the surface’s smoothness Light that hits a rough surface is reflected in many directions. This is called diffuse reflection. Light reflected off a smooth surface is called specular reflection.

Reflected Angles Angle of Incidence: The angle between a ray that strikes a surface and the normal to that surface at the point of contact.

Angle of Reflection Angle of Reflection: The angle formed by the line normal to a surface and the direction which a reflected ray moves. Go to the following link for an animation http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/optics/lr.html

Incoming and reflected angles Incoming and reflected angles are equal Law of Reflection: The angle of incidence= the angle of reflection

Reflection Rules The image is said to be a virtual image Left right reversal: if you raise your left hand, you will notice that the image raises what would seem to be it's right hand. Image is upright instead of inverted- there is no top-bottom vertical reversal. If you stand on your feet in front of a plane mirror, the image does not stand on its head. For plane mirrors, the object distance (often represented by the symbol do) is equal to the image distance (often represented by the symbol di). the dimensions of the image are the same as the dimensions of the object. If a 1.6-meter tall person stands in front of a mirror, he/she will see an image which is 1.6-meters tall.

Concave Mirrors A concave mirror is an inwardly curved mirrored surface that is a portion of a sphere that converges (come together) incoming light. Concave mirrors create a magnified image How big the image appears depends on how curved the mirror R= radius of curvature C= center of curvature

Real Images A real image is an image formed when rays of light actually intersect at a single point A real image is a clear and crisp image that is formed Image location can be predicted from the mirror equation: 1/p + 1/q = 1/f P= object distance, q= image distance, f= focal length

Calculating magnification Unlike flat mirrors, the images formed are not the same size as the original image. How big or small they appear can be calculated by the following equation: M= h’/h=q/p M= Magnification h’= image height h= object height q= image distance p= object distance

Convex Mirrors Convex mirrors are outwardly curved mirrors that is a portion of a sphere that diverges incoming light rays The image appears smaller The focal point and center of curvature are behind the mirror’s surface A virtual, upright image forms where three rays meet Magnification for convex mirrors is always less than 1.

Concave vs. Convex mirrors

Convex mirror images

Telescopes One type of telescope uses curved mirrors and small lenses to form an image. This is called a reflecting telescope. Another type of telescope uses only lenses to form an image and is called a refracting telescope