# Physics Paper 2 Questions and Answers - Achievers Joint Mock Exams 2023

Instructions

• Answer all the questions in section A and B
• All working must be clearly shown.

## QUESTIONS

SECTION A (25MKS)

1. Figure 1 below shows an object O placed in front of a plane mirror. A ray of light is drawn coming from object O and striking the mirror at P. After striking the mirror, the ray of light is reflected

1. Which of the four dots represents correct position of the image of O? label this dot Q (1mk)
2. By drawing a line on the diagram above to represent ray at P, mark the angle of reflection and label it r. (1mk)
2. A charged conductor is slowly brought near the cap of a positively charged electroscope. The leaf first collapses and then diverges. State the charge on the conductor (1mk)
3. Give a reason why it is necessary to leave the caps of the cells open when charging an accumulator. (1mk)
4. Figure 2(a) and 2(b) below shows a simple experiment using a permanent magnet and two metal bars A and B. The permanent magnet was placed close to the iron fillings as shown in Fig 2(a) and then removed. The metal bars attracted the iron filings as shown in Fig 2b.

State with a reason which bar is made from a soft magnetic material (2mks)
5. Figure 3 below shows two parallel current carrying conductors P and Q placed close to one another. Current flows in the opposite directions

Sketch on the figure the magnetic field pattern formed by the two conductors (1mk)
6. Figure 4 below shows two identical lamps lamps L1 and L2 connected to a battery
.
1. Using an arrow, indicate on the diagram above the direction of the convectional current (1mk)
2. State the effect if any, of closing switch S on L1 (1mk)
7. Figure 5 below shows a ray light incident on water-kerosene interphase
State which one of the two liquids has a higher absolute refractive index (1mk)
8. The table in figure 6 below shows part of the electromagnetic spectrum in order of decreasing wavelength.

1. How are waves C produced? (1mk)
2. State one use of the wave D (1mk)
9. The source of sound and two listeners are position close to a tall building as shown in the fig.7

1. State the property of sound by which Listener A is able to hear the sound produced (1mk)
2. Listener B is moving directly towards Listener A and has a problem hearing the sound produced. Explain (2mks)
10. A house has a lighting circuit operated from a 240V mains supply. Four bulbs rated 40W, 240V and six bulbs rated 100W, 240V are switched on for 5 hours a day. Determine the monthly bill for the consumer given that the cost of electricity is at Kshs.5.50 per unit.
(Take 1 month= 30 days and the standing charge is sh.150) (3mks)
11. State two properties of x-rays similar to those of visible light. (2mks)
12. State any one condition under which a pinhole camera may form an image on its screen which has the same size as the object. (1mk)
1. Define the term work function (1mk)
2. Explain how the intensity of radiation affects the photo-electric effect (1mk)
13. Figure 8 below shows an eye defect

Use a ray diagram to show how the defect above could be corrected (2mks)

SECTION B (55 MARKS)

1.
1. An object O stands on the principal axis of a concave mirror as shown in figure 9 below

1. By drawing suitable rays, show the position of the image (3mks)
2. Determine the magnification of the image formed (3mks)
2. In experiment to determine the focal length of a concave mirror, a group of form two students collected some data and used the results to plot the graph shown in figure 10 below.

Using the graph above, determine:
1. The object position when the image position is 45cm (2mks)
2. Slope of the graph (3mks)
3. The focal length of the mirror. (2mks)
2.
1. Students set up a mass attached to a spring such that when it oscillates it taps on water surface in a wide shallow tank as shown in figure 11 below.

The students measured time for 20 oscillations and found that the mass takes 36 seconds
Determine
1. The periodic time of mass (2mks)
2. The frequency of the waves produced on the water surface (1mk)
3. The speed of the waves if the students counted four ripples between the mass and end B of the tank (3mks)
2. State any one factors that would increase the speed of sound in air (1mks)
3. It was noted that for the circuit diagram below when S was open the voltmeter gave a reading of 12V but when the switch was closed the voltmeter reading drops to 10V.

1. Explain why there is a difference in the reading on the voltmeter when the switch is open and when it is closed. (2 mks)
2. Name one example of a non ohmic coductor (1 mk)
3. If the ammeter gave a reading of 0.8A when S is closed, determine the value of R. (2 mks)
3.
1.
1. Define capacitance of a capacitor. (1mk)
2. Figure 12 below shows a pair of parallel plates of a capacitor connected to a battery

State with a reason the effect of moving the positive plate on the capacitance. (2mks)
1. Vertically downwards
2. Horizontally to the left (2mks)
2. The circuit diagram in figure 13 below shows four capacitors connected between two points A and B

1. Determine the capacitance across AB (3mks)
2. Calculate the total energy stored in the 4μF capacitor (3mks)
4.
1. A student is provided with two resistors of value 2Ω and 6 Ω
1. Draw a circuit showing the resistor connection that provides the greatest current flow (2mks)
2. Calculate the total resistance of the circuit (assume negligible internal resistance) (2mks)
2. Given that the battery in your circuit in a(i) has an e.m.f of 3V and internal resistance 1.2Ω. Calculate the current through
1. The 6Ω resistor (3mks)
2. The 2Ω resistor (2mks)
5. The graph in the figure 14 below shows the relationship between the attractive forces of an electro magnetizing current

1. Give reasons for the shape of the graph by domain theory (3mks)
2. On the same fig.14, sketch a graph for the case where the soft iron core is replaced with steel. (2mks)
3. Two similar razor blades were placed one on a wooden block and the other on an iron block as shown in figure 15.

Fig. 15
State and explain the observation on the razor blade;
1. On the iron block (3mks)
2. On the wooden block (2mks)

## MARKING SCHEME

SECTION A ( 25 MARKS )

1. r tracing back to image (2mks)
2. Negative (-ve) (1mk)
3. During charging, oxygen and hydrogen gases are produced which should escape through those openings (1mk)
4. B.
Loses its magnetism faster thereby becoming weaker hence attracting fewer iron filings (2mks)

5. pattern direction (2mks)

1.  (1mk)
2. Becomes dimmer  (1mk)
6. Kerosene  (1mk)
Produced by hot bodies such as the sun, mercury vapour lamps and electric arc sparks. (1mk)
• Used to detect broken bones, abnormal growths
• Detects flaws in metal casting and welded joints.
• Used in the study of crystal structure. (Any 1) (2mks)
1. Diffraction (1mk)
2. Interference.  (2mks)
The two opening acts as two source two source hence the two waves interfere producing soft and loud sound along the way.
7. Daily consumption
Monthly consumption
Monthly bill
3mks
• They are transverse waves
• Can be reflected, diffracted,
• They obey the wave equation v=f -refracted and exhibit interference.
• They can travel in a vacuum
• They can be plane polarized (2mks) any 2
• When the size of object equals to the size of the screen
• when object distance from pinhole eqals to the length of the camera (1mk)
8. a-minimum energy required to dislodge an electron from a metal surface.
b- increases the number of photoelectrons produced (1mk) any 1

9. Lens refraction eye lens refraction to retina (2mks)

SECTION B MARKS

1.
1.

1. Both rays Virtual image (2mks)
2. Magnification = image height = 2.8√ = 2.545√ Object height 1.1
NB: Image and object heights must be measured accurately. (2mks)

2. (2mks)

1. When v= 45cm, magnification = 2.45 √ from the graph
But magnification = v/u
2.45= 45/u
u = 18.37cm.
2. Slope (2mks)
3. Focal length = 1
Slope
= 1
=0.075
= 13.3cm√ (1mk)
2.
1.
1. T = 36/20
=1.8 sec. (2mks)
1. Frecuency =1/T
=1/1.8=0.5556ΗΖ

2. 3 λ=800/3 = 266.7m
But v = f λ
= 0.5556 x 266.7m√
= 148.2m/s (2mks)
2.
• Wind blowing in the direction of sound
• High humidity
• Increase in temperature √ - Decrease in density of air √
• Increase in pressure as a result of increased temperature.
3.
1. 12v is the e.m.f while 10v is the terminal voltage due to the voltage drop.
2. diode,torch (2mks)
3. v=IR R=10/0.8
=12.5 Ω
3.
1.
1. Charge per unit voltage OR Charge storing ability of a capacitor (1mk)
2.
1. the distance between the plates is reduced, hence the capacitance of the capacitor is increased√ (2mks)
2. Area of overlap decreases √hence capacitance decreases. (2mks)
3. Upper wing:
1⁄2 + 1 ⁄4 = 3⁄4 = 1 ⋅ 333μF
Lower wing :
1 + 3 = 4μF
Combined capacitance = (1. 333 + 4)μF = 5.333 μF (4mks)
2. = 4 ⋅ 5VC = 4 × 10−6
E = ½CV2 = ½ × (4.5 × 10−6) × 42 = 3.6 × 10−5   Joules (3mks)
4.
1.

1. (2mk)
2. RT = R1 + R2 = (2 + 6 ) = 8 (2 mks)
2.

1. R=(8+1.2)=9.2Ω1
I = = 3 =0.3261A (2mks)
g   9⋅2
(3 mks)
2. same current flows since it’s a series connection=0.3261A (2 mks)
5.
1. When current increases , the dipoles align themselves until all of them are in the same perfectly aligned direction i.e magnetic saturation  The magnet force of attraction becomes constant  (3 mks)

2. ( 2mk)
3.
1. The razor blade remain attracted to the iron block
The magnet induces magnetism into the razor blade which in turn induces the iron block to acquire opposite polarity.Since the attraction between the blade and the magnet is equal to the attraction between the blade and the iron, the blade does not move(3 mks)
2. The blade is attracted by the magnet.
No magnetism is induced into the wooden block and so the razor Attraction is only between the blade and the magnet (3 mks)

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