Physics Paper 2, May/June. 2011  
Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main
General Comments
Question 13

  1. (i)    What is an eclipse?
    (ii)    List the three types of eclipse
  2. A student in a lecture theatre can read from the board clearly but requires a pair of spectacles to read from a book.
     What eye defect has this student?
     What type of lens is needed to correct the eye defect?
    The focal length of the lens used to correct this defect is 10 cm. Calculate the   power of the lens. 
  3. A car B moves towards a stationary car A.  If B produces an ultrasonic sound at a point and it takes 5.6 x 10-3  s for a beep to be heard in B, calculate the distance between the two cars at that instant.  (Speed of sound in air = 340 ms-1) 
  4. The image of an object is located 9 cm behind a convex mirror.  If the magnification produced is 0.6, calculate the focal length of the mirror.




In part (a) almost all candidates that attempted the definition got it wrong; However, many candidates were able to list the three types of eclipse correctly.
In part (b) (i) & (ii), performance was above average. In part (iii) performance was fair.  Some   candidates however have problems converting to metres and also the stating the correct unit of power of a lens.
In part (c), candidates are expected to make use of the concept of echo where V =  .  However performance was low because of lack of comprehension of the question
In part (d) Performance  was fair.

The expected answers are:

(a)(i)   An eclipse is a shadow resulting from the obstruction of light from the sun by either
  the moon or the earth.
     (ii)   -    Solar eclipse (eclipse of the sun)
   -    Lunar eclipse(eclipse of the moon)
   -    Annular eclipse

(b)(i)   The eye defect
   Long sight (hypermetropia)/hyperopia
    (ii)   The type of lens
  Convex/converging lens

   (iii)    Power of lens
   Power  =  1/f


   =      +  10 dioptre (D)

(c)    V  = 

         d  =  

                     =    0.952m
        (d)       M =                         

                  0.6  =                     =

                   u  =  15 cm                    = 

                                          f  =  -22.5cm

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