## Physics Paper 2 Questions and Answers - Londiani Joint Mock Exams 2022

QUESTIONS

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

1. Figure 1 below shows a ray of light incident on a mirror surface and making an angle of 750 with the horizontal. The mirror is then rotated through 300 in clockwise direction. Determine the angle between the incident ray and the new reflected ray. (3 marks) 2. Give a reason why increase in leaf divergence is the only sure way to determine the sign of charge on a body. (2 marks)
3. Fig 2 shows the features of a dry Lĕclanche cell. 1. State the polarity of the part labeled A. (1 mark)
2. State the role of the chemical substance B (1 mark)
4. Figuee 3 below shows two parallel magnets with unlike poles adjacent to each other. Sketch the magnetic field pattern around the magnets. (2 marks) 5. Figure 4 below shows the image, I, formed by a concave mirror. Locate using ray diagrams the position of the object. (2 marks) 6. The set up in figure 5 below can be used in a laboratory for lifting and releasing a steel ball. 1. State the material which is suitable for use in the core. (1 mark)
2. If a slightly larger ball is to be lifted, it is necessary to make an electromagnet stronger. Name two ways of increasing the strength of the magnet. (2 marks)
7. Figure 6 below shows a sketch is a displacement – time graph of a wave traveling at 320ms-1 the wave takes 1.2 seconds to move from point A to B. Calculate the wavelength of the wave. (3 marks) 8. An echo sounder produces a pulse and an echo is received from the seabed after 0.4 seconds. If the speed of sound in water is 1500m/s, calculate the depth of the sea bed. (2 marks)
9. Figure 7 represents two parallel plates of a capacitor separated by a distance d. Each plate has an area of A square units. State any other adjustment other than the area and distance that can be made so as to increase the effective capacitance. (1 mark)
10. The figure 8 below shows the path of a ray of light passing through a rectangular block of Perspex placed in air. Calculate the refractive index of Perspex. (3 marks)
11. The figure 9 below shows sound waves emitted by a drum struck. Explain why the wave fronts are directed to the ground. (2 marks)

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

1.
1. Study the circuit diagram in figure 10 and answer the following question 1. Calculate the effective resistance of the circuit. (3 marks)
2. Determine the current through the 3 Ω resistor (4 marks)
2. State ohms law (1 mark)
3. Eight dry cells can be arranged to produce a total e.m.f of 12v just like a car battery.
1. Determine the e.m.f of an individual cell (1 mark)
2. Explain why it is possible to start a car with the lead acid accumulator, but not with the eight dry cells in series. (2 marks)
4. 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 11 below. 1. Draw the circuit diagram you would use for the experiment. (1 mark)
2. Explain how the resistance of the bulb changes (2 marks)
2. Figure 12 shows a current carrying coil in a magnetic field. The direction of the current and the resulting force are shown. 1. State the importance of using the split rings instead of complete rings. (1 mark)
2. Indicate the polarity of the magnets if the force developed acts as shown in the diagram. (1 mark)
3. Explain how reducing the distance between the poles of the magnet would affect the operation of the system (3 marks)
4. State two factors that would be altered to change speed of the coil (2 marks)
3.
1. In an experiment to observe interference of light waves a double slit is placed close to a monochromatic source of light as shown in figure 13. 1. State the function of the double slit (1 mark)
2. State what is observed on the screen (1 mark)
3. State what is observed on the screen when the slit separation S1S2 is reduce. (1 mark)
4. Explain how the observation in (ii) above is obtained (2 marks)
2. Figure 14 shows a stretched string AB vibrating in its fundamental mode. 1. Determine the frequency of the sound it produces given that sound travels at 340m/s in air. (3 marks)
2. Distinguish between node and antinode. (2 marks)
4.
1. State two laws of refraction of light (2 marks)
2. A student carried out and experiment on refraction of light incident on a glass block. She obtained the following values of I and r and proceeded to fill the corresponding columns of sine I and sine r as shown below.
 i r Sin i Sin r 20º 12.7º 0.34 0.22 30º 18.9º 0.50 0.32 40º 25.0º 0.64 0.42 50º 30.0º 0.77 0.50 60º 34.0º 0.87 0.56 70º 37.0º 0.94 0.60
She then drew the graph of sin i (y – axis) against sin r as shown in the figure 15 below. From the graph
1. Determine the slope of the graph. (3 marks)
2. State what the value in b(i) represent. (1 mark)
3. Use the results in b (i) to calculate the velocity of light in glass, given that velocity of light in vacuum is 3.0 x 108 m/s. (3 marks)
3. A ray of light travels from air into medium 1 and 2 as shown in figure 16 below Calculate the refractive index of medium 2 relative to Medium 1 (1n2) (2 marks)
4. A ray light is incident at right angles at the face AB, of a right-angled isosceles prism of refractive index 1.6 as shown in the figure 17 below. If the prism is surrounded by a liquid of refractive index 1.4. Determine:
1. The angle of incidence on the face BC. (1 mark)
2. The angle of refraction on the face BC. (2 marks)
5.
1. State the law of electrostatic charge. (1 mark)
2. A small chain is often seen hanging at the back of a petrol carrying lorry. State and explain its significance. (1 mark)
3. The figure 18 below shows an uncharged pith ball under the attraction of a charged ball. State and explain what would be observed after the two-pith ball touch. (2 marks)
4. The figure 19 below shows a negatively charged rod placed near an uncharged conductor resting on an insulation support. 1. Show the charge distribution on the conductor. (1 mark)
2. State the effect;
1. Of momentarily touching the conductor with a finger while the charged rod is still near the conductor. (1 mark)
2. On the charge distribution of withdrawing the negatively charged rod after momentarily touching the conductor. (1 mark)
5. The figure 20 below shows a charged rod held close to the cap of an uncharged leaf electroscope. If the cap is momentarily earthed before removing the charged rod, what charge is left on the electroscope? (1 mark)
6. Figure 21 represents a step in charging a material B negatively by induction. 1. What is the charge on A? (1 mark)
2. Explain what happens at C. (1 mark) ## MARKING SCHEME

1. Angle of reflection 15°✓
The reflected angle = twice angle of rotation
= 30 × 2 = 60°✓
Angle between incident and new reflected ray = 15° + 15° + 60°
= 90°✓
2. Decrease in leaf divergence is between unlike charges and also between charged material and uncharged charged materials ✓
While increase in leaf divergence is only possible between two like charges ✓ Hence the only sure way.
3.
1. Negative
2. Ammonium chloride solution converts zinc to zinc chloride.
4. 5. 6.
1. Iron
2. Increasing the number of turns on the magnetic core
Increasing current
7. Period= 1.2? ÷ 3 complete waves = 0.4?✓
V = wavelength x frequency or
V = wavelength ÷ period
Wavelenggth = = 320 × 0.4?✓
= 128m✓
8. speed = 2d/t
d = speed x time
2
= 1500 × 0.4
2
= 300 ?
9. Nature of the dielectric.
10. ƞ =   1
Sin C
=     1
sin 42.5
= 1.48
11. This is because the ground is cooler than the air above it. Sound waves from the drum are refracted towards the ground.
12.
1.
1. 1/R = ½ + 1/3 + 1/6
= 1Ω
RT = 4 + 1
= 5Ω
2. I = 3/5
= 0.6A
Voltage across the 3Ω resistor = 0.6 x 1.0
= 0.6V
Current I = 0.6/3
= 0.2A
2. Current flowing through a conductor is directly proportional to the potential difference across its ends provided that the temperature and other physical conditions are kept constant.
3.
1. e.m.f of 1 dry cell = 12/8
= 1.5V
2. When eight dry cells are joined in series, the internal resistance of the combination becomes very high. Due to this internal resistance, small current will be drawn from it.
4.
1. 2. Opposition offered by electron to the flow of current causes heating effect which increases the temperature of the filament hence higher resistance.
13.
1. Ensures the current flows in one direction continuously.
2. Left - south pole
right - north
3. The speed of the coil increases. Decrease in distance between the poles increases the strength of the magnetic fields hence greater force experienced on the conductor.
4. Varying the size of the current in the circuit and varying the strength of the magnet.
14.
1.
1. To act as coherent source of light.
2. A series of alternating bright and dark fringes are observed on the screen.
3. The number of fringes decrease while their size increase.
4. S scatters light that strikes it, illuminating S1 and S2, which further scatters light. On the screen, a sequence of dark and light bands are created by the superposition of the diffracted light from S1 and S2.
2.
1. l = ½λ
λ = 21
2 x 0.66
= 1.32
But v = λf
f = v/λ
= 340/1.32
= 257.58Hz
2. Nodes are points in a stationary wave that are at rest while antinodes are points on a vibrating string with maximum amplitude.
15.
1. The incidence ray, the refracted ray and the normal at the point of incidence all lie on the same plane.
The ratio of the sine of the angle of incidence, i, to the sine of the angle of refraction, r, is a constant for a given pair of media.
2.
1. Slope = Δsin i
Δsin r
0.64 - 0.34
0.42 - 0.22
0.3/0.2
= 1.5
2. The refractive index of the glass block.
3. ƞ =  velocity of light in air
velocity of light in gas
1.5 = 30.0 x 108
x
x = 2.0 x 108 m/s
4.
1. 45º
2. n1sinθ1 = n2sinθ2
sin r = 1.6 x sin45
1.4
r = 53.9º
16.
1. Unlike charges attract, like charges repel.
2. Earthing. The chain expels charges from the tanks thus preventing explosion.
3. The balls will repeal because the other ball gets charged through contact thus acquire similar charge.
4.
1. 2.
1. The conductor is earthed
2. The positive charges will be distributed uniformly throughout the conductor.
5. Negative charge
6.
1. Positive charge
2. Earthing. Negative charges from the earth neutralizes the repelled positive charges.

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