PHYSICS PAPER 2 - 2019 LANJET JOINT MOCK EXAMINATION

SECTION A: (25 MARKS)
ANSWER ALL QUESTIONS IN THIS PAPER.

1. State what happens to the depletion layer when:
   1. A diode is forward biased.                                                           (1 mk)
   2. A diode is reverse biased.                                                          (1 mk)

2. Explain why a plain sheet of paper and a plane mirror both reflect light yet only the plane mirror forms images while a paper cannot form images              (2 mks)

3. Explain how x-rays are produced.                                                                                     (1 mk)

4. State one similarity and one difference between cathode rays and x-rays.                       (2 mks)

5. The figure below shows an arrangement for lighting three lamps; A, B and C only one which controlled directly by the switch.
   
   
   1. Which of the lamps is directly controlled by the switch?                                        
   2. What is the name given to this use of an electromagnet?                                     
   3. Which lamps can be on at once?                                                         
   4. Explain how lamp C comes in.                                                                            

6. Figure 2 below shows an object P placed inside a soft iron ring and a strong bar magnet.  Use the information to answer questions 6 and 7.
   
   Name the process shown in the diagram.                                                                   (1 mk)

7. Indicate on the diagram, the magnetic field pattern.                                                         (1 mk)

8. A concave mirror produces a real image 2cm tall of an object 5.0mm tall placed 10cm from the mirror.  Find the focal length of the mirror       (2 mks)

9. The velocity of light in glass is 2.0 x 10⁸m/s.  Calculate the angle of refraction in the glass for a ray of light passing from air to glass at an angle of incidence of 40^o.  (3 mks)

10. The figure below shows a tuning fork producing waves.  The wave fronts are as in the diagram.
    
    If the speed of sound in air is 330m/s, determine the value of d.                                   (3 mks)

11. A convex lens forms an image four times the size of the object on a screen.  If the distance between the object and the screen is 10cm, determine;
    The image distance.                                                                                               (2 mks)
    Focal length of the lens.                                                                                       (2 mks)

SECTION B: (55 MARKS)
ANSWER ALL THE QUESTIONS FROM THIS SECTION.

12.  
    1. A TV tube uses a voltage of 4550V to accelerate electrons released from its cathode by thermionic emission.
       1. What is meant by thermionic emission?                                                                (1 mk)
       2. Figure (a) and (b) shows the screen, Y-gain and time base controls from a typical oscilloscope displaying a wave form. 
                                                        
    2.  
       1. From the display waveform, state the period the trace.                            (1 mk)
       2. Calculate the frequency of the waveform.                                               (2 mks)
    3. Ultraviolet radiation incident on a zinc plate releases electrons from the zinc surface.  The energy of each incident proton is 5.4eV.  Zinc has a work function of 4.3eV.
       1. State the name given to this effect.                                                           (1 mk)
       2. What is meant by work function of the metal?                                        (1 mk)
    4. An electron is emitted from the surface of zinc.
       1. Calculate the maximum kinetic energy of the electron in Joules.             (2 mks)
       2. Calculate the maximum speed of the electron. ( M_e = 9.11x10^-31 kg)     (2 mks)

13.  
    1. State Lenz’s law of electromagnetic induction.                                            (1 mk)
    2. The primary coil of a transformer has 1200 turns and the secondary coil has 60 turns.  The transformer is connected to a 240V a.c source.
       Determine:
       1. The output voltage.                                                                                   (2 mks)
       2. The output current when the primary coil has a current of 0.5A (Assume there is no energy losses). (3 mks)
       3. One of the primary ways in which power is lost in transformers is through eddy currents. State how eddy currents can be minimized.  (1 mk)
    3. Consider the table below for electromagnetic waves. 
       

       Radiation	Production	Detection	Application
       Radiowaves	A	Aerials	B
       D	Thermal vibration of atoms of hot bodies.	C	Imaging/medical diagnosis

              
       1. Fill in the spaces labeled.                                                                           (4 mks)
       2. State one similarity between ultraviolet rays and gamma rays in terms of their dangers.             (1 mk)

14.  
    1. The cell in the figure below has an e.m.f of 2.1V and negligible internal resistance.
       
       Determine:
       1. The total resistance in the circuit.                                                                          (2 mks)
       2. Current in the circuit.                                                                                           (1 mk)
       3. The reading of the voltmeter.                                                                              (2 mks)
    2.  
       1. The circuit below shows a lighting circuit for a house. Mention any two mistakes in the wiring circuit.              (2 mks)
          
    3. A house has four lamps rated (60W, 240V), a cooker rated (5Kw, 240V and an iron box rated (1Kw, 240V).  All are used for 3.5 hours a day.  Calculate the monthly cost for electricity for the owner at the rate of 13.5 cents/KWhr.  (3 mks)
    4. An electric heater is rated 1KW, 240V.  If the element is connected to 240V mains supply for 10 minutes, determine the amount of heat dissipated.                                  (2 mks)

15.  
    1. Describe the steps followed to charge an uncharged gold leaf electroscope positively given a negatively charged polythene rod.        (3 mks)
    2. The figure below shows three capacitors of capacitance 3  connected to a 12.0V supply.
       
       Calculate:
       1. The total capacitance of the circuit.                                                                      (2 mks)
       2. The charge through the 2.0                                                      (3 mks)
    3. Give two factors that increase the capacitance of a parallel plate capacitor.    (2 mks)

16.  
    1. The figure below shows a transverse wave. Calculate the frequency of the wave.                                                                         (2 mks)
       
    2. A boy standing in front of a cliff blows a whistle and hears the echo after 0.5seconds.  He then moves 17 metres further away from the cliff and blows the whistle again.  He now hears the echo after 0.6 seconds. Determine the speed of sound in air.     (3 mks)
    3. The element Thorium is radioactive.  It decays by emitting Beta particles.                       
       Determine the  number of the protons and neutrons in the nucleus formed when a Thorium atom emit a beta  particle.   (2 mks)
    4. The figure below shows a source of beta particles and a detector being used to check the thickness of paper in a paper mill.
       
       
       1. Explain how the device works.                               (2 mks)
       2. Explain why beta particles are used instead of alpha particles or gamma rays.(2 mks)