## Physics Paper 2 Questions and Answers - Bungoma Diocese Mock Exams 2021/2022

INSTRUCTIONS TO CANDIDATES:

• This paper consists of two sections A and B.
• Answer all questions in Section A and B in the spaces provided below all questions.
• All working MUST be clearly shown.
• Non-programmable silent electronic calculators and KNEC Mathematical tables may be used.
Take g = 10Nkg-1

SECTION A (25 MARKS)
Answer ALL questions in this section in the spaces provided

1. Figure 1 below shows a ray of light incident to the first of the two mirrors inclined at an angle of 60°. Complete the path of the ray after reflection from the mirror. (1mk) 2. Figure 2 below shows a positive charge near a plate carrying negative charge. Draw the electric field between them. (2mks) 3. Two pins are hanging from a magnet S shown in diagram below figure 3. Explain why the nails do not hang vertically downwards. (2mks)
4. Draw diagrams to illustrate what happens when plane waves are incident on a slit.
1. When the width of the slit is large compared with the wavelength of the waves.   (2mks)
2. When the width of the slit is small compared with wavelength of the waves. (2mks)
5.
1. Arrange the following waves in order of decreasing wavelength; x-rays, infrared, microwaves and visible light. (1mk)
2. State one application of visible light. (1mk)
6. State one defect of a simple cell and explain how it can be controlled. (2mks)
7. A girl shouts and hears an echo after 0.6 seconds later from a cliff. If velocity of sound is 330m/s, calculate the distance between her and the cliff. (3mks)
8. Determine the reading of the ammeter in figure 4 below. (2mks) 9. A ray of light is incident on a glass-oil interface as shown in fig. 5 below. Determine the value of r. (Take refractive index of glass and oil as 3/2 and 8/5 respectively) (1mk) 10. State two factors that affect the capacitance of a parallel-plate capacitor. (2mks)
11. state two advantages of an alkaline accumulators over the lead acid accumulators 2mk
12. An electric bulb is rated 40W ,240v .what is the resistance of the filament 2mks

SECTION B (55 MARKS)
Answer ALL the questions in this section in the spaces provided

1.
1. Study the circuit diagram below and answer the questions that follow. 1. Calculate the effective resistance of the circuit. (3mks)
2. Find the voltmeter reading. (3mks)
2. A cell drives a current of 3.2A through a 2.8Ω resistor. When it is connected to 1.6Ω resistor, the current that flows is 5A. Find the E.m.f. (E) and internal resistance of the cell. (4mks)
2.
1. Complete the diagram below indicating the rays that will lead to the formation of the image shown below (3marks) 2. A compound microscope with an objective lens Lo of focal length 1.2cm and an eye piece lens Le of focal length 2.8cm. An object is placed 1.8cm from the objective lens. The system of lenses produces a final image a distance of 12.0cm from Le. Determine the distance of separation of lens Lo and Le. (4 MARKS)
3. An object is placed 12cm from a convex lens and it forms a virtual image 36cm from the lens. Calculate the focal length of the lens. (3 MARKS)
4. The graph below shows the variation of potential difference V with current I for a certain cell. From the graph determine
1. The internal resistance of the cell (3 marks)
2. The e.m.f of the cell (1 mark)
3.
1.
1. State one cause of energy losses in a transformer and explain how it can be minimized. (2mks)
2. Describe briefly the energy changes involved in the generation of electrical energy at a hydropower station (2mks)
3. What are the advantages of transmitting power at:
1. Very high voltages (1mk)
2. Alternating voltage (1mk)
2.
1. Explain how electrons are produced in a cathode ray oscilloscope (CRO) (2 mk
2. State two functions of the anodes in a CRO. (2mks)
3. At what part of the cathode ray oscilloscope would the time base be connected ( 1mk)
4. State why the tube is highly evacuated (1mk)
4.
1. Define the term supersonic speed as used applied in sound waves ( 1mark )
2. In an experiment to determine the speed of sound in air, a drum at a point 150 m from a vertical wall was struck at varying frequencies while listening to the echo .The echo coincided with sound from the drum at a time when 20 successive strikes were made within a time of 18.5 s.
1. Determine the time taken for the echo to heard 3marks
2. Determine the speed of sound in air at the place 2marks
3. What difference would you expect if the experiment was repeated on a colder day  1mark
3. A boy strikes a railway with a hammer. A railway worker 600 m away hears two sounds,One from the railway and the other from the air .If the time intervals between the two Sounds is 1.65s and the speed of sound in air is 340m/s, determine the speed of in the Railway line. 4 marks
5.
1. define the term eclipse of the moon 1 mark
2. differentiate between umbra and penumbra as used in the eclipse 2marks
3. an incident ray forms an angle of 45 degrees with the mirror at point of incidence .The position of the incident ray is kept constant while the mirror is rotated at an angle of 20 degrees .Find the angle through which the reflected ray is rotated 2 marks
4. A tree 25 m high stands , 50 m in front of a pinhole camera whose screen is 30 cm behind the pinhole. What is the height of the image of the tree formed on the screen . 3mks ## MARKING SCHEME

SECTION A

1. 2. 3. They acquire North Poles at the ends thus they repel.
4.
1. 2. 5.
1. Microwaves, infrared, visible light, X-rays.
2.
• Observing objects
• Taking pictures.
6.
1. polarization -use potassium dichromate
2. local action - use pure zinc metal
7. V = 2S => S = Vt
t                2
S = 330 x 0.6 = 99m
2
8. I = V/R
2/61/3
=0.33A
9. Ang = 3/2   ano = 6/3
Ong = ana  ang = 5/8 × 3/215/16 = 0.9375
Sin 60 = 0.9375 ⇒ Sin r =  0.866  = 0.9237
Sin r                                   0.9375
r = 67.47°
10.
• Distance between the plates.
• Area of plates.
• Dielectric material used.
11.
• Alkaline produces higher current
• Lasts longer
• It is portable
• Less maintenance and care.
12. p = v2/R
40 w = ( 240v )2/R
R = 57600
40
= 1440Ω

SECTION B

1.
1.
1. Parallel 1/R1/61/41/8
1 = 2 + 3 + 4
R         12
1/R = 9/12
R = 4 = 11/3Ω
Rt = 4 + 11/3
= 51/3Ω
2. V = IR
I =   4.5
R     5.33
= 0.844A
V = 4 x 0.844
= 3.377V
2. E = 3.2r + 2.8 (3.2)    E = 5r + 5 (1.6)
E = 3.2r + 8.96          E = 5r + 8 = …
Solve 1 & 2 simultaneously
r = 0.533Ω                  E = 10.67V
2.
1. Complete the diagram below indicating the rays that will lead to the formation of the image 2. A compound microscope with an objective lens Lo of focal length 1.2cm and an eye piece lens Le of focal length 2.8cm. An object is placed 1.8cm from the objective lens. The system of lenses produces a final image a distance of 12.0cm from Le. Determine the distance of separation of lens Lo and Le. (4 MARKS)
1/v1/f − 1/u1/1.2 − 1/1.81/v = 0.2778, v = 3.6cm
ue = d − v
1     =  1  −
d−3.6    2.8   10
d − 3.6=3.8889
d = 7.489cm
3. An object is placed 12cm from a convex lens and it forms a virtual image 36cm from the lens. Calculate the focal length of the lens. (3 MARKS)
u = 12cm
v = −36cm
f =  uv
u+v
12x − 36432 = +8cm
12 − 36      24
4. The graph below shows the variation of potential difference V with current I for a certain cell.
From the graph determine
1. The internal resistance of the cell (3 marks)
internal resistance, r  =      1     12 − 8 = 2.857-1, 0.35 ± 0.01
2. The e.m.f of the cell (1 mark)
e.m.f when I = 0 e.m.f = 6.8V
3.
1.
1. State one cause of energy losses in a transformer and explain how it can be minimized. (2mks)
Causes                                                Method of minimising
Eddy currents                                        Laminations
Hysterises loss/Magnetic reversals       Use of soft iron
Heating effect (T2R)                              Use of thick copper wires
Magnetic flux leakage                            Winding secondary on primary/use of soft iron core
Any one, with correct method (2mks)
2. Describe briefly the energy changes involved in the generation of electrical energy at a hydropower station (2mks)
Potential energy → kinetic energy → electrical energy
3. What are the advantages of transmitting power at?
1. Very high voltages (1mk)
• To minimize power loss;
2. Alternating voltage (1mk)
• Can be stepped up or stepped down;
2.
1. Explain how electrons are produced in a cathode ray oscilloscope (CRO) (2mk)
• The cathode is heated by filament and electrons are released from cathode ray by thermionic emission
2. State two functions of the anodes in a CRO (2mks)
• to accelerate the electrons
• to focus the electrons towards the screen
3. At what part of the cathode ray oscilloscope would the time be connected (1mk)
• Across x-plate
4. State why the tube is highly evacuated (1mk)
• To reduce collision/interaction/interferance of electrons, (hence ionization) with air molecules in the tube
Or
• To maintain K.E or minimise loss of K.E
4.
1. the speed of an object that exceeds the speed of sound
2.
5.
1. an eclipse of the moon occurs when the earth comes between the moon and the sun.
2. umbra is a type shadow that occurs when no light reaches the screen while penumbra is a type of shadow that occurs when some light reaches the screen
3. 20 x 2
= 40 degrees
4. ho =25 m, u = 50 m, v = 30 m
( ho )= 50 m
hi      30 m
hi = 750/50
= 15 m

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