Physics Paper 2 Questions and Answers - Bondo Joint Mocks Exams 2022

Questions

Instructions to Candidates

• This paper consists of two sections; A and B
•  Answer all the questions in section A and B in the spaces provided
• All workings must be clearly shown in the spaces provided below each question
• Non programmable silent electronic calculators may be used.
• Candidates should answer the questions in English

SECTION A (25marks)
Answer all the questions in this section in the spaces provided

1.  Figure 1 below shows a plan view of an object O in front of a plane mirror
   
   Which one of the reflected rays of light P, Q, R and S appears to come from the image of O (1 mark)
2. Figure 2 below shows an uncharged pith ball A under the attraction of a charged ball B.
   
   State and explain what would be observed after the two pith ball touch each other (2 marks)
3. Figure 3 below shows the features of a dry Leclanche cell.
   
   State the function of the part labelled X (1 mark)
4. What is meant by the term “lost volts” as used in cells (1 mark)
5. Figure 4 below shows a longitudinal wave that takes 0.5s to move from point A to B and at a speed of 36m/s.
   
   Calculate the frequency of the wave (2 marks)
6. Figure 5 represents an object O and the image I formed by a concave mirror.
   
   By suitable rays, determine the focal length of the mirror. (2 marks)
7. Figure 6 shows white light falling on a prism as indicated.
   
   
   1. Name the colour at X and Y (2 marks)
   2. What measurable quantity is associated with colour of light? (1 mark)
8. Explain how hammering demagnetizes a magnetized iron bar (2 marks)
9. Figure 7 shows a standing wave on a string, fixed at both ends.
   
   Explain how the standing wave is generated. (3 marks)
10. Figure 8 below shows a positive charge near a plate carrying negative charge.
    
    Draw the electric field between them. (2 marks)
11. Figure 9 represents part of electric cooker coil.
    
    
    1. Why is the material labeled X is coiled? (1 mark)
    2. State the property of material X that makes it suitable for its use. (1 mark)
12. State two factors affecting the type of shadow formed by an object placed in front of a source of light. (2 marks)
13. The graph below shows radioactive decay of iodine.
    
    Use the graph to determine the fraction of the amount remaining after 16 days. (2 marks)

SECTION B (55 marks)
Answer all the questions in this section in the spaces provided

14.      
    1. In the setup below, the suspended meter rule is in equilibrium balanced by the magnet and the weight shown. The iron core is fixed to the bench.
       
       
       1. State and explain the effect on the meter rule when the switch K is closed. (3 marks)
       2. What would be the effect of reversing the battery terminals? (1 mark)
    2. Figure 12 shows three resistors connected as shown.
       
       If the voltmeter, V reads 4V, find the Potential difference across the 8Ω  resistor. (3marks)
    3. A student stands some distance from a high wall and claps her hands.
       1. What two measurements would he need to make in order to determine the speed of sound? (2 marks)
       2. Show how you would make use of these measurements to determine the speed of sound in air (1 mark)
15.  
    1. Students wanted to determine the focal length of a convex lens of thickness 0.6cm using an optical pin and a plane mirror. Figure 13 shows the experimental set up used when there was no parallax between the pin and the image.
       
       
       1. Use the setup to determine the focal length of the lens. (2 marks)
       2. Explain how you arrive at your answer. (2 marks)
    2. An Image, I 15cm tall stands vertically on the principal axis of a convex lens of focal length 10cm and at a distance of 20cm from the lens as shown in figure 14 below.
       (the graph is drawn to scale)
       
       
       1. By ray construction, complete the diagram to show the position of the object (3 marks)
       2. Determine the size of the object (1 mark)
       3. Determine the object distance (1 mark)
16.       
    1. For a particular bulb, a series of readings of the current through the bulb for different potential differences across it is taken and plotted as shown in figure 15 below.
       
       
       1. Draw the circuit diagram you would use for the experiment. (3 marks)
       2. Explain how the resistance of the bulb changes (1 mark)
    2. The figure 16 below shows a capacitor C being charged.
       
       
       1. State what would be observed on the ammeter when the switch is closed: (1 mark)
       2. Explain how the capacitor is charged. (3 marks)
17.  
    1. What is meant by donor impurity in a semiconductor? (1 mark)
       
    2.       
       1. State the observation made on L 1 and L 2 when switch K is closed. (1 mark)
       2. Account for the observation made above. (1 mark)
    3. You are provided with a diode, a resistor R, an a.c source of low voltage and connecting wires. In the space provided, sketch the circuit diagram for a half-wave rectifier and indicate the terminals where the output voltage v 0 may be connected. (2 marks)
    4.  
       1. Alpha particles (µ) are more ionizing than Beta (b) particles. Give two reasons for this. (2 marks)
       2. Fig shows the path of radiation from a radioactive source after entering a magnetic field.
          The magnetic field is directed into the paper and is perpendicular to the place of the paper shown in the figure.
          
          
          1. Identify the radiation. (1 mark)
          2. Give a reason for your answer. (1 mark)
18.      
    1. A surface whose work function is 2.46eV is illuminated by light of frequency 3x10 15 Hz. Calculate the maximum kinetic energy of the ejected photoelectrons.
       ( h = 6.63 x 10 -34 js and e = 1.6 x 10 -19 C). (3 marks)
    2. A monochromatic beam of radiation is directed on a clean metal surface so as to produce photoelectrons. Give a reason why some of the ejected photoelectrons have more kinetic energy than others. (1 mark)
       
    3.        
       1. Figure below shows an electric generator. The points P and Q are connected to a cathode Ray oscilloscope (C.R.O)
          Sketch on the Axis provided the graph of the voltage output as seen on the C.R.O, given that when t= o, the coil is at the position shown in the figure (1 mark)
          
       2. The emf generated by a.c generator is represented in the graph in Figure 20.
          
          Give reasons for the changes in the emf as the coil rotates from 0 0 to 90 0 and 90 0 to 180 0 . (3 marks)
          1. An immersion heater rated 3000W is used continuously for 45 minutes per day.
             Calculate the cost per week at 60cts per unit. (2 marks)
19.    
    1. Figure 21 shows the electric wiring of an electric cooker. X, Y and Z are main wires.
       
       Identify the wires Y and X (2 marks)
    2. What adjustment on the x-ray tube will;
       1. Increase the hardness of the x-rays (1 mark)
          1. Reduce the intensity of the x-rays. (1 mark)
    3. A CRO screen with 1cm squares displays the trace in figure 22 below.
       
       The Y- gain is set 0.5v/cm and the time base is set at 5ms/cm. Determine
       1. the voltage (1 mark)
       2. the frequency of the signal (3 marks)
    4. Figure 23 shows as simple form of cathode ray tube, which produces a sharp shadow of a Maltese cross on a screen.
       
       What property of cathode rays does the figure 23 above illustrate (1 mark)

Marking Scheme

1. R
2. The balls will repel
   B will share its net charge with A hence like charges repel
3. It acts as a depolarizer / to help stop gas forming
4. It is the potential drop in a cell due to internal resistance of the cell
5. T = 0.5/2.5 = 0.2s
   ⸫ f = 1/T = 1/0.2 = 5Hz
6.  
     
   the reflected ray passing thro’ F at O
7.    
   1. X – Red
      Y – Violet
   2.  Wavelength
8.  
   – Hammering disturbs/ loosens the dipoles
   - Hence losing their orientation
9. - waves produced are reflected at the fixed points
   - Incident and reflected waves interfere constructively at the antinodes
   - And destructively at the nodes
10.    
      
11.      
    1. - coiling increases the length hence resistance to increase the heating effect of electric current.
    2. – high melting point
12. – size of the object
    - Distance between the source of light and the object
13. – Amount remaining after 16 days = 190g
    ⸫ Fraction remaining after 16 days = 190/400 = 19/40
14.      
    1.      
       1. –the meter rule tilts to the side with the magnet
          - the iron core is electrically magnetized with the end near the magnet acquiring S-pole
          - hence attracts the magnet and metre rule downwards
       2. – the end of the iron core near the magnet acquires N-pole and repels the magnet making the metre rule to tilt to the side of the suspended weight.
    2. – current through 6Ω resistor = V/R = 4/6 = 0.6667A
       - current through 3Ω resistor = V/R = 4/3 = 1.3333A
       ⸫ Total current through 8Ω = 0.6667 + 1.3333 = 2A
       Voltage across 8Ω = IR = 2 x 8 = 16V
       
       OR
       R_Parallel = 6 x 36 + 3 = 189 = 2 Ω
       Current flowing in the circuit = V/R = 4/2 = 2A
       Voltage across 8Ω = IR = 2 x 8 = 16V
    3.      
       1. –distance between the student and the wall
          - time taken for the echo to come back to him
       2. Speed of sound is calculated as V =       2   x    distance between student and wall      
                                                                            time taken for the echo to come back
15.            
    1.         
       1. f = 20 + 0.62 = 10.3cm
       2. - Rays from the object pass through the lens and are refracted parallel to the principal axis
          - The parallel rays are then reflected back by the mirror to the lens which converge them to a point that coincides with the object.
    2.        
       1.     
          
       2.  -ho = 15cm
       3. v = 20cm
16.         
    1.            
       1.          
          
          The circuit diagram must be Workable
       2. Resistance increases with increase in temperature
    2.     
       1. the ammeter reading reduces from maximum to zero
       2.  
          • electrons move from negative terminal of the cell to B
          • at the same time electrons move from plate A to the positive terminal of the Cell
          • equal amounts of positive and negative charges are stored in plate A and B respectively
    3.      
       1.      
          • Is the pentavalent atoms that donates free electrons to a semiconductor during Doping.
       2.  
          • - L1 lights while L2 does not
          • -when the switch is closed D1 is forward biased while D2 is reverse biased
       3.  
       4.      
          • Alpha is more massive hence collides with more air molecules
          • Alpha is slow moving in air hence takes more time in air
       5.  
          1. Beta particle
          2. because of motor- effect / Flemings Left Hand Rule
17.       
    1. hf = θ + eV
       6.63 x 10-34 x 3.0 x 108 = 1.6 x 10-19 x 2.46 + K.E
       K. E = 1.989 x 10-18 - 3.936 x 10-19
       K. E = 1.5954 x 10-19 J
    2. due to varying photon energies / different photons have different energies
    3.         
       1.   
           
          at least 2 crests
       2.    
          1. from 0ᵒ - 90ᵒ magnetic flux linkage changes from high to low/decreasing
          2. From 90ᵒ - 180ᵒ magnetic flux changes from low to high/increasing
          3. At 0ᵒ and 180ᵒ magnetic flux change is maximum though in different directions
    4. Cost = Kwh x unit cost = 3 x 45/60 x 7 x .60 = ksh 9.45
18.       
    1.   
       1. X – Live wire
       2. Y - Earth wire
    2.    
       1. increasing the accelerating voltage / potential difference between cathode and anode
       2. Reducing the filament / cathode current
    3.  
       1. Voltage = 4cm x 0.5V/cm = 2V
       2. 1/2 T = 8cm 5ms/cm = 40ms
          ⸫ T = 40ms x 2 = 80ms = 0.08s
          f = 1/T = 1/0.08 = 12.5Hz
    4. cathode rays travels in straight lines