Department of Natural Sciences

                                             Clayton College & State University

 

April 14, 2003

 

Physics 1112 – Quiz 9b

 

 

Name  ___SOLUTION__________________________________

 

 

 A youngster looking into the shiny concave 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.

 

    1. Where will the image of her nose appear?

 

R = +5.00 cm (concave 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 =  0.360 cm –1

          

           q =  2.78 cm

 

    1. Find the magnification.

 

M = -q/p = -(2.78 cm)/(25.0 cm) = - 0.111

 

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

 

Real (q > 0), inverted (M < 0), and reduced (|M| < 1).

 

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