Mirror Equations Unit 3 Light Mirror Equations Symbols

Mirror Equations Unit 3: Light

Mirror Equations � Symbols ◦ ◦ ◦ ◦ used: Ho- height of the object Hi- height of the image m-magnification do (or p)- distance between object and vertex di (or q)- distance between image and vertex f- focal length R- radius of curvature (2 F)

Equations � Magnification= � Curved m= mirror and lens equation:

Sign conventions 1. ◦ ◦ 2. 3. 4. 5. ◦ ◦ ◦ Focal length (f)- Positive for converging mirrors Negative for diverging mirrors Object distance (do)- is positive Image distance (di)Positive for all real images Negative for all virtual images Heights (Ho and Hi)Positive if upright Negative if inverted Magnification (m)- Positive image is upright Negative image is inverted

� Note: sign conventions are needed to get the correct answer when using mirror equations

To solve equations � Write down what you know and what you need to find � Draw a quick sketch � Find which equation has only one unknown; use this value to solve for other unknowns � Check to make sure answer fits with sketch

Example #1 �A object 8. 0 cm high is placed 30 cm in front of a converging mirror with a focal length of 20 cm. Determine the image location, magnification and image height. � Draw a sketch � Write what you know � Write what you are looking for � Write equation � Substitute numbers in

Answer

Solution #1

Example #2 � An object 12. 0 cm high is placed 10 cm in front of a diverging mirror with a focal length of 4 cm. Determine the image location and height.

Solution

assignment � Complete practice problem- following slide � When done get answer checked and move on to the- Converging and Diverging mirror equation problems

Practice problem 1. A candle 3. 0 cm high is 30. 0 cm from a converging mirror that has a focal length of 20. 0 cm. a) Where is the image located? b) What is the height of the image?