Reflection & Mirrors There are two kinds of mirrors Plane mirrors Curved mirrors Concave (Converging mirrors) Convex (Diverging mirrors)

Images formed by plane mirrors

Characteristics of images formed by plane mirrors Image size = object size Image is virtual (not real; hence lines behind mirror are broken) Image is upright (Erect)

Concave mirrors

Concave as converging mirror F Principle axis

The three rays of light 1. Ray parallel to the principle axis gets reflected through the Focal point 2 1 Principle axis C F 2. Ray through the Focal point gets reflected parallel to the principle axis. 3 3. Ray through C gets reflected alone the same path.

Images formed by concave mirrors When Object is between mirror and F C F F C

Images formed by concave mirrors When Object is at F C F F C

Images formed by concave mirrors When Object is at C gets reflected C F F C

Images formed by concave mirrors

Convex mirrors Wide view

Convex mirrors Diverges rays of light

Images formed by convex mirrors Image Characteristics Are virtual Smaller Behind the mirror

Images formed by convex mirrors When Object is between c and F C F F C

magnification We determine the magnification of the image using the formula;

The mirror formula

Image distance di

Homework Textbook pg 460 # 1-7

Problem solving Using the mirror formula

Example Jose places an object 3 cm away from a concave mirror whose focal length is 10 cm. calculate the image distance. 1/f =1d0+1/di 1/10=1/3 + 1/di 1/di = 1/10-1/3 1/di = -7/10 di=-10/7= -1.43 cm

Class work Workbook Pg 175 # 5-8, Workbook pg 180 # A-1 to A-5

Refraction of light Refraction is the bending of a wave when one part of the same wave travels faster (or slower) than another part. Pencil appear bent because of refraction The waves are faster in air than in water causing our eyes to see the pencil that appear bent.

Refraction of light in glass Light Bends when it passes the boundary line between two media

Refractive index (n) Refractive index (n)  also called index of Refraction, is the measure of bending of a ray of light when passing from one medium into another. Refractive index of any medium is given by the following formula: Where speed of light in a vacuum C =3.0x108m/s

Refractive indices for different substances

Snell’s Law

Question What is the speed of light in water? (water; n=1.33)

Question A beam of light that is traveling through air strikes flint glass at an angle of 30.0° to the normal. At what angle does the beam enter the flint glass? (Flint glass; n=1.656 and Air; n=1)

Total internal reflection

Total internal reflection When total internal reflection takes place, the incident angle 1 is called the Critical angle c Snell’s law becomes n1sinc=n2sin 900

Homework Textbook pg 461 # 11-21

Class work Workbook pg 179 # 9-12, pg 180 # A6-A10