Optics Mirrors and Lenses

Topics for Optics Reflection of LightReflection of Light –Law of Reflection –Plane Mirrors –Concave Mirrors –Convex Mirrors Refraction of LightRefraction of Light –Law of refraction –Convex lenses –Concave lenses Optical InstrumentsOptical Instruments

Reflection: occurs when a wave strikes an object and “bounces” off. ALL waves show reflection. WAVE PROPERTIES OF LIGHT – General Info

Light reflected off a smooth or shiny surface is reflected in one direction. SPECULAR REFLECTION

Light reflected off a rough surface is reflected in many directions. DIFFUSE REFLECTION

Normal: is a line perpendicular to the surface of the mirror. Incident Ray: is the ray of light that is striking the mirror. Reflected Ray: is the ray of light that bounces off the mirror.

Angle of Incidence is the angle between the normal and the incident ray. Angle of Reflection is the angle between the normal and the reflected ray.

Law of Reflection -Mirrors All mirrors obey the Law of reflection The angle of incidence equals the angle of reflection

Law of Reflection Law of Reflection (Cont.) It does not matter the shape of the mirror, the angle of reflection will still equal the angle of incidence.

Mirror Characteristics: Real or Virtual Upright or Inverted Reduced or Enlarged

Real or Virtual Real images can project on a screen Virtual images can only be seen in a mirror

Upright or Inverted Upright images are oriented the same as the object Inverted images are oriented in the opposite direction as the object

Reduced or Enlarged Reduced images are smaller in size than the object Enlarged images are larger in size than the object

Plane Mirrors The image formed by plane mirrors can only be seen behind the mirror. This is known as a virtual image. Image is the same size as the object. Only the right and left of the image is changed.

Curved Mirrors Curved mirrors can be either –concave (making a little cave) –convex (vexing out in the middle)

Location of Image f = focal length d o = distance of object d i = distance of image

Concave Mirrors Converge Rays of Light

Ray Tracing Basics All rays parallel to the principle axis will go through the focal point. The rays are also reversible, so if they start at the focal point, they will hit the mirror and go parallel to the principle axis.

Ray Tracing Basics C: Center of Curvature F: Focal Point (1/2 of C)

Ray One: Draw a parallel line from the top of the object to the mirror. This line should bounce off the mirror and through the focal point.

Ray Two: Draw a line from the top of the object through the focal point to the mirror. This line should bounce off the mirror and go parallel to the principle axis.

Ray Three: Draw a straight line from the top of the object and through the Center of curvature.

Reviewing the three rays: 1.Parallel, then through f. 2.Through f, then parallel. 3.Straight line through top of object and C.

Final step: Draw the image where the 3 lines converge… Make sure the bottom of the image is on the principle axis, and the top of the image is at the convergence point.

Distant Objects: The image of a distant object will form at the focal point of the concave mirror and be very very small.

Objects At C: The Image will be: RealSame location as object Inverted Same size

Objects Between C and f: The Image will be: RealImage is located outside C Inverted Enlarged size

Objects Inside f: The Image will be: Virtual Upright Enlarged in size

Convex Mirrors Diverge Rays of Light

Ray Tracing for Convex Mirrors Very similar to ray tracing for concave mirrors, except the object is on the other side of the mirror then the Center of curvature and focal point…

Ray One: Draw a parallel line from the top of the object to the mirror. An imaginary line should be drawn from this point to the focal point.

Ray Two: Draw a line from the top of the object to the focal point on the other side of the mirror, but stop at the mirror. Draw a line parallel to the principle axis from the point where the previous line hits the mirror.

Ray Three: Draw a straight line from the top of the object and to the Center of curvature.

Reviewing the three rays: 1.Parallel, then through f. 2.Through f, then parallel. 3.Straight line through top of object and C.

Final step: Draw the image where the 3 lines converge…