PHYSICS PAPER 2 - KCSE 2019 JOINT PRE MOCK EXAMINATION NAMBALE

SECTION A (25 MARKS)

1. State two differences between images formed by a plane mirror and a pinhole camera.
2. You are provided with connecting wires, 2 dry cells, a switch and two bulbs. Draw a circuit diagram to show; cells in parallel, bulbs in parallel and controlled by one switch.   (2marks)
3. When an ebonite rod is rubbed using a dry clothe it acquires negative charge.
   Explain how the negative charge is acquired.                                         (1mark)
4. The diagram below shows a soft Iron bar placed between poles of a magnet. Draw the magnetic field pattern produced.       (2mks)
   
5. The diagram below shows a conductor in a magnetic field.
   
   Indicate on the diagram the direction of motion.                            (1mark)
6. State one application of total internal reflection.                           (1 mark)
7. You are provided with resistors of 2.0Ω, 4.0Ω and 9.0Ω. Draw a circuit diagram to show how the three resistors can be connected together to give an effective resistance of 6Ω. (2 marks)
8. The diagram below shows plane waves moving from shallow to deep end of a pond.
   
   
   1. Complete the diagram to show the waves on the deep end.                   (1 mark)
   2. State what happens at the boundary to:
   3. The frequency of the waves, (1 mark)
   4. The speed of the waves. (1mark)
9. The figure below shows a simple cell.
   
   
   1. Identify solution A. (1 mark)
   2. When switch K is closed, the bulb lights brightly initially, but grow dim and dimmer until it goes off;
      1. State the possible cause of this behavior.               (1 mark)
      2. State the remedy for the behavior.                             (1mark)

10. The diagram below shows a wave profile.
    
    Determine the frequency of the wave.                 (3 marks)
11. The diagram below shows a system of capacitors.  
    
    Calculate the effective capacitance between the points A and B.   (3mks)
12. A driver was given two mirrors – a plane mirror and convex mirror to choose from. He chose convex mirror as his driving mirror. Give two reasons why?
    
    SECTION B: 55 MARKS
    
    
13.  
    1. State Snell’s law of refraction.               (1mark)
    2. In an experiment to determine the refractive index of a liquid, the liquid was poured into a measuring cylinder, a pin was placed at the bottom of the cylinder and another pin used to locate the apparent position of the first pin. The values of real and apparent depth were used to plot a graph as shown below.
       
       
       1. From the graph determine the refractive index of the liquid.     (3 marks)
       2. Given that the velocity of light in vacuum is 3.0 x 10⁸ m/s, what would be the velocity of light in the liquid above.     (2marks)
    3. The diagram below shows a ray of light incident on a glass-air interface. 
       
       Given that the refractive index of glass is 1.4, determine the value of θ     (3marks)
    4. State two conditions necessary for total internal reflection to occur.        (2marks)
    5. The diagram below shows a ray of light incident a glass prism ABC at 90^o 
                                          
       Complete the ray to show how it emerges from the prism given the critical angle of the glass is 42^o.(2marks
14.  
    1. State Ohm’s law.                                                                                                    (1mark)
    2. You are provided with three resistors R₁, R₂, and R₃ connected in parallel. If the Pd across them is V, derive an expression for the effective resistance of the three resistors.
    3. The diagram below shows the resistors R₁, R₂ and R₃ connected in a circuit.
       
       R1 = 4Ω
       R2= 3Ω
       R3=6Ω
       1. Calculate the total resistance in the circuit.                          (2marks)
       2. The total current flowing in the circuit.                                 (2marks)
       3. The pd across resistor R₁              (2 marks)
       4. The current flowing through resistor R₂ (2marks)
    4. State two factors that affect the resistance in a conductor. (2marks)
15.  
    1. Explain how the following affect the velocity of sound in air. (3mks)
       1. Wind
       2. Temperature
       3. Humidity
    2. A girl standing in a gorge between two cliffs claps her hands at a steady rate ad hears two echoes. The first eco comes after 2 seconds and the other after 3 seconds. If the speed of sound is 340m/s, what is the distance between the cliffs.      (3marks)
    3. The diagram below shows part of electromagnetic spectrum. 
       

       Grama Rays

       A

       B

       Visible light

       C

             
       1. State which property of the electromagnetic waves decrease in the direction given. (1mk)
       2. Name the wave marked B. (1 mark)
       3. State any one use of A. (1mark)
       4. State how C is detected. (1mark)
16.  
    1. Define Principal focus of a biconcave lens.                                             (1mark)
    2. The diagram below shows a virtual image of an object placed in front of a biconvex lens. 
       
       Draw appropriate rays to locate the object.     (2marks)
    3. A convex lens forms a red image five times the size of the object n a screen. If the distance between the object and screen is 120cm, determine;
       1. Image distance (1marks)
       2. Focal lent of the lens.                                                                                       (3marks)
    4. The diagram below shows a defect in human eye   
                                           
       1. Name the defect. (1mark)
       2. State two causes of the defect.  (2marks
       3. How can the defect be corrected? (1mark)
17.  
    1. State any two ways of increasing the capacitance of a parallel plate capacitor. (2marks)
    2. The diagram below shows a simple network of capacitors. If the potential difference between X and Y is 12V.
       
       Calculate the total charge stored by the capacitors.  (3mks)
       If the potential difference between X and Y is 12v, calculate the total charge stored by the capacitors.                     (3marks)
    3. State any one application of capacitors.                 (1mark)

MARKING SCHEME

1.  
   

   plane mirror	pinhole camera
   -the image is virtual -the image is upright( erect)  -same size as object	-the image is real -the image is inverted smaller than the object

2. bulbs in parallel
   cells in parallel
   
3. the piece of cloth donates or loses electrons to the ebonite rod, the sirplus electrons makes ebonite negatively charged
4.  
   shape direction
5.  
    
6. used in optic cables
7.  
    
8.  
   1.  
       
   2.  
      1. remain the same
      2. increases
9.  
   1. dilute sulphuric acid
   2.  
      1. polarization
      2. adding a depolariser
10. T= 0.025
    f= 1/T = 1/0.02 = 50Hz
11.  
     
12. -Convex mirror has a wider field of view
    -the image formed is usually diminished  into the mirror regardless of the position of the object
13.  
    1. the ratio of the sine of the angles of incidence to that of the sine of the angle of refraction is constant
    2.  
       1. gradient = 2/3 
          n = 1/gradient = 1/(2/3) = 1.5
       2. n= (velocity of light in vaccum)/ ( velocity of light in liquid) 
          = (3 ×10⁸) /2.5  = 2.0 × 10⁸
    3.  
        
    4. -light must be travelling from a denser medium to a less dense medium
       -the angle of incidence in the denser medium must be greater than the critical angle
    5.  
        
14.  
    1. the current flowing hrough a conductor is directly proportional to pd across it provided the temp and othe physical conditions are kept constant
    2. since resistors is parallel, total current I_T divides into I₂, I₁, I₃
       
    3.  
        
    4. -Temp of the conductor
       -cross-sectional area/diameter/thickness of the conductor
15.  
    1.  
       1. wind- wind blowing in the same direction increases the velocity of sound, the reverse is true
       2. temperature- sound travels faster in hot air than cool air
       3. humidity - velocity of sound increases with humidity
    2.  
        
    3.  
       1. the wavelength
       2. B- ultra violet
       3. A is X rays 
          -cancer therapy
          -crystallography
          -screening of laggages at the airport
          -x-ray photography
       4. C- infra red- detected by bolometer , thermometer, with blackened bulb, thermopile of skin
16.  
    1. it is that point on the principal axis from which rays parallel and close to the principal axis appear to diverge after refraction by lens
    2.  
        
    3.  
        
    4.  
       1. myopia
       2. long eyeball
          short focal length
       3. use diverging lens
17.  
    1. -increase the area of plate overlap
       -reduce distnce between plates
       -use a dielectric og greater permitivity
    2.  
        
    3. -smoothing circuits
       -reduction of sparking in induction coil
       -in tunning circuits
       -in camera flash