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Chapter 36. Image Formation 1: Flat mirror Spherical mirrors. Find the image, method 2, the mirror/lens equation. When a spherical mirror is given, we know its radius R .
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Chapter 36 Image Formation 1: Flat mirror Spherical mirrors
Find the image, method 2, the mirror/lens equation When a spherical mirror is given, we know its radius R. Under paraxial condition, the angle is small, and from the law of reflection and focal point definition, we have That is the focal length is N V for a converging mirror.
From the ray diagram to mirror equation Objective: Find the equation that connects object distance, image distance and the focal length. Oh A hO I V hI O B Ih So: Triangle and are similar: Triangle and are similar:
From the ray diagram to mirror equation Oh A From hO And : I V One has : hI O B Ih
Converging spherical mirror formulas Object distance, image distance and focal length: Focal length and sphere radius: Object distance, image distance and magnification:
From converging mirror to diverging mirror: change signs • These sign conventions apply to both concave and convex mirrors • The focal length has a different sign convention: • The equations used for the concave mirror then applies to the convex mirror. Converging Diverging
Sign Conventions, Summary Table Image smaller Image same size Image larger
Convex mirror, only one case: virtual image, not inverted, smaller Formulas to be used: One has the following: virtual image Image not inverted Image smaller than object
Concave mirror, object 5 locations Formulas to be used: Case 1: One has the following: Real image Image inverted Image smaller than object (Case 2 to 5 will be left as homework)
More examples • You use a concave mirror to make a fire with the sun light. The focal length of the mirror is 20 cm. You hold it towards the sun and try to light a small wood stick at its tip. Where you want to place this tip?
More examples • When you look into a flat mirror, the image distance is the same as the object distance. The rear review mirror on the side of your car is a convex mirror with a focal length of -0.60 m. If a truck is 10.0 m from this mirror, what is the size of the truck image compare with the actual truck?