Department of Natural Sciences

                                             Clayton College & State University

 

April 14, 2003

 

Physics 1112 – Quiz 9a

 

 

Name  _____SOLUTION________________________________

 

 

 A youngster looking into the shiny convex back of a spoon with a spherical bowl sees herself reflected therein. The bowl has a radius of 5.00 cm and her nose is 25.0 cm from its surface. (Hint: A convex mirror has a negative focal length.)

 

    1. Where will the image of her nose appear?

 

R = -5.00 cm (convex mirror)       p = + 25.0 cm (the object is in front of the mirror)

 

f = R/2                 

 

f =  (-5.00 cm)/2 = - 2.50 cm  

          

           1/p + 1/q = 1/f        1/q  = 1/f – 1/p

          

           1/q = 1/(-2.50 cm) – 1/(25.0 cm) =  -0.400 cm –1 – 0.040 cm –1 =  -0.440 cm –1

          

           q = - 2.27 cm

 

    1. Find the magnification.

 

M = -q/p = -(-2.27 cm)/(25.0 cm) = 0.091

 

 

    1. Describe the youngster’s image (real or virtual, upright or inverted, enlarged or reduced?

 

Virtual (q < 0), upright (M > 0), and reduced (|M| < 1).

 

 

    1. Draw a ray diagram to check your answers to the previous questions.