Physics Paper 2 Questions and Answers - Form 4 End Term 2 Exams 2023

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INSTRUCTION TO CANDIDATES

This paper consists of TWO sections: A and B
Answer ALL questions in section A and B in the spaces provided.
ALL workings MUST be clearly shown.
Mathematical tables and electronic calculators may be used.

SECTION A 25MARKS

At what angle should two plane mirrors be inclined at to produce 5 images? (2marks)
In a simple cell consisting of copper and zinc plates, bubbles of gas are seen forming around the copper plate
1. What is the name given to this defect (1mk)
2. Suggest how the defect you have named in 1 (i) above can be minimized (1mk)
In an experiment to determine the focal length of a converging lens using the lens formula, several values of image distance corresponding to value of object distance U were determined and a graph of magnification m against image distance v, plotted as shown in Figure 11 below

The equation of the graph can be represented by the equation
m = ^v/_f − 1
1. What does the gradient of the graph represent? (1mk)
2. Determine the focal length of the lens. (2mks)
One way of magnetizing a magnet is hammering. Explain how the magnetization is achieved (2marks)
Figure below shows a solenoid wound on a soft iron core

State the polarities at point A and B when the switch is closed (2mark)
Figure below shows a circle with two diodes P and Q and a cell:-

Explain the observation which would be made if S is closed (2mks)
The following is a part of a radio – active series.

Identify the radiation r, find the values of c and d. (3 marks)
State one reasons why Alluminium is preferred to copper in transmission of power ( as overhead cables) (1mark)
Define the term ‘wavelength’ of a transverse wave (1mark)
A boy standing 400m away from a cliff claps his hands and hears an echo 2.5s late
Velocity of light in water is 2.2×10⁸m/s while in glass velocity is 2.0×10⁸m/s. Calculate the angle of incidence in water which could produce an angle of 300 in glass (3marks)
The figure 10 below shows a current carrying conductor
1. On the same diagram draw, the magnetic field pattern produced. (1mk)
2. State one possible rule that can be used to predict the field direction produced in the above diagram. (1mk)
State one advantages of using a convex mirror as a driving mirror. (1mk)
Table below shows part of the electromagnetic spectrum

Microwave Infra-red Visible light A X-ray

Name part labelled A (1mark)

SECTION B 55 MARKS

The figure below represents a cathode ray oscilloscope (C.R.O). use it to answer the questions that follows.
1. Name the parts labelled A and B. (2mks)
2. What are the functions of parts labelled C and D? (2mks)
3. Explain how electrons are produced . (1mk)
4. Give a reason why the tube is evacuated. (1mk)
5. The potential between the anode and the cathode of an X-ray tube is 80kv. Calculate;
  1. The energy of an electron accelerated in the tube. (Electronic charge e = 1.6 x 10-19 C) (3mks)
  2. The velocity of electrons in the tube. (Mass of an electron = 9.11 x 10-31kg ) (3mks)
1. The refractive index of glass is³/₂ and that of water is ⁴/₃ . Calculate the refractive index of glass with respect to water. (2 mks)
2. The figure below shows a ray of light incident at an angle of 35.6° at point D on the first face of a glass prism ABC. The refractive index of the prism is 1.6.
  1. Determine the angle of refraction at point D. (2 mks)
  2. Find the angle of incidence of the refracted ray on the face AC to 1 decimal point. (2 mks)
  3. Complete the ray diagram to show the emergent ray from the face AC. (2 mks)
  4. State two conditions necessary for total internal reflection to occur. (2 mks)
1. State one application of a capacitor. (1 mk)
2. Figure 7 shows four capacitors connected to a battery of 12 volts.
  
  Calculate:
  1. Effective capacitance. (2 mks)
  2. Charge on 3.2µF (2 mks)
  3. Potential Difference across 5µF (2 mks)
  4. The energy stored by 2µF (2 mks)
3. What are effects on capacitance of a parallel plate capacitor when :
  1. Increasing the area overlap of the plates ? (1mk)
  2. Increasing the distance of separation between plates ? (1mk)
4. The cell in figure 10 has an e.m.f of 2.1 V and negligible internal resistance.
  
  Determine the
  1. Total resistance in the circuit (2 marks)
  2. Current in the circuit (1 mark)
  3. Reading of the voltmeter (2 marks)
1. State Lenz’s law of electromagnetic induction. (1mk)
2. The figure shows two coils of insulated copper wires wound on a single soft iron core. One coil is connected to a battery through a switch and the other is connected to a resister through a galvanometer.
  
  It is observed that as the switch is closed, the pointer of the galvanometer deflects momentarily. The same as when the switch is opened.
  1. Explain why the pointer deflects momentarily. (2mks)
  2. State one way in which the current through R can be increased. (1mk)
3. 1. State one way in which power is lost in a transformer. (1mk)
  2. A transformer uses 240V ac supply to deliver 9A at 80V to a heating coil. If 10% of the energy taken from the supply is lost in the transformer itself, What is the current in the primary winding? (2mks)
The diagram below shows simplified diagram of an x-ray tube,
1. Name the parts A, B, and C. (3mks)
2. What adjustments would be made to:
  1. Increase the penetrating power of the x-rays produced. (1mk)
  2. Increase the intensity of the rays produced. (1mk)
3. Name a suitable material for the part marked B and give a reason for your choice. (2mk)
4. Name a suitable material for the part marked C and state its purpose. (2mk)
5. Why is it necessary to maintain a vacuum inside the tube? (1mk)
6. In a certain X- ray tube electrons are accelerated by p.d of 12 kV. Assuming all energy goes to produce X-rays, determine the frequency of the X-rays produced
  (Planck’s constant =6.63x10^-34 Js. Charge of an electron=1.6x10^-19C) (3 mks)

MARKING SCHEME

SECTION A

n = ³⁶⁰/_? - 1 √1
S = 360
? -1
θ = 360
6
= 60°√1
1. Polarization√1
2. Add a depolarizer/ an oxidizing agent√1
1. Reciprocal of the focal length power of the lens
2. ¹/_f = gradient => f = ¹/_gradient
  f= 13cm
- Hammering makes the dipoles to vibrate√1
- Earth magnetic field aligns the dipoles√1
- B- North pole√1
- A- South pole – Allow correct pole at one end
A1 will shows a reading while A2 will not show any reading. This is the fact that P will be forward biased hence conducting while Q is reverse biased hence it wil not conduct.
r =beta particle ✔, c=206 ✔ d= 82 ✔
- It forms a coating at the surface to prevent rusting and as an insulator
- It is less dense hence easy to carry
- It is easily available/cheaper (Any TWO √1 each)
Distance between a particle in the wave medium and the next one that is in phase with it or Distance between two successive crest/trough √1
V = 2nd
t
= 400 × 2
2.5
= 320m/s
n=(2.2x108)/(2.0x108)
=1.1
= sin i
sin 30
Sin I = 1.1 x sin30
= 0.55
I = sin^-1 0.55
2. - Right hand grip rule
  - Maxwell – cork screw rule
- Wide view
- Gives upright image
ultra violet light
1. - A – Grid✔1
  - B – Electron gun✔1
2. - C – Vertical deflection of beam of electrons✔1
  - D – Horizontal deflection of beam of electrons✔1
3. By thermionic emission or heating the filament✔1
4. To prevent ionization of electrons as they move to the anode✔1
5. 1. E = ev✔1
    E = 1.6 x 10-19 x 80000✔1
    = 1.28 x 10-14 J✔1
  2. ½ mv² = 1.28 x 10^-14✔1
    v² = 2 ×1.28 × 10^-14
    9.11 ×10-31
    v = √2 ×1.28 ×10-14
    9.11 ×10-31 ✔1
    v = 2.23 x 10⁸ ms✔1
1. _wη_g = _wη_a × _aη_g
  = ³/₄ × ³/₂
  = ⁹/₈
  = 1.13
2. 1. η = Sin i
    Sin r
    1.6 = Sin 35.6°
    Sin r
    r = 21.3º
  2. Angle of incidence = 38.7º (show working)
    Sin C = ¹/_η = ¹/_1.6
    = 38.7º
  4. - The critical angle must be exceeded. ✓¹
    - Light must be travelling from a dense medium to a less dense medium. ✓¹
1. Capacitors are used in
  - rectification smoothing circuits
  - tuning circuits
  - camera flash
  - reduction of sparking in induction coil contact
    any one 1
2. 1. 2 x 8 = 16 = 1.6μF
    2 + 8 10
    1.6 + 3.2 = 4.8μF ✔
    C_T = 5 x 4.8 ✔ = 24 = 2.45 x 10^-6F ✔
    5 + 4.8 9.8
  2. Q = CV
    = 2.45 x 10^-6 x 12 = 2.94 x 10^-5C ✔
    charge on 3.2μF = ²/₃ x 2.94 x 10^-5 = 1.96 x 10^-5C ✔
  3. p.d on 5mF = Q = 2.94 x 10^-5 = 5.88volts ✔
    C 5 x 10^-6
  4. energy = ¹/₂CV² ✔
    = ½ x 2 x 10^-6 x 6.12²= 3.75 x 10^-5J ✔
3. 1. Capacitance will also increase
  2. capacitance will decrease.
4. 1. Parallel circuit ¹/₃₀ + ¹/₂₀ = ⁵/₆₀ or ⁶⁰/₅₀R = 12 Ω
    Total resistance = 10 + 12 = 22Ω (2 marks)
  2. l = ^V/_R = ^2.1/₂₂ = 0.095A (1 mark)
  3. Reading of the voltmeter
    V = lR = 10 x 2.1 = 0.95 (2 marks)
    22
1. Lenz’s Law states that the direction of induced current is such that it opposes the charge producing it.✔
2. 1. When switch S is closed, the magnetic field strength increases (magnetic flux) from zero to maximum ✔½This changing magnetic flux (field) induces an e.m.f in the secondary coil ✔1 When the switch is opened, the magnetic field strength decreases (magnetic flux) from maximum to zero ✔½This produces an induced current in the secondary coil
  2. Having more turns on the coil connected to the cell ✔
3. 1. - Hysterisis
    - Eddy currents
    - Resistance of wire
    - Loss of magnetic flux linkage
  2. Power Primary x ⁹⁰/₁₀₀ = VsIs ✔1
    240 x IP x ⁹⁰/₁₀₀ = 80 x 9
    IP = 80 × 9 × 100 ✔1 = 3.33A ✔1
    240 90
1. A – cathode B – Anode C – Cooling fins
2. 1. increase the p.d at the anode (B)
  2. increase the cathode heater current
3. Tungsten:- It has a high melting point so the heat produced will not melt it easily
4. Copper – it is used to cool/conduct heat away from the anode
5. So that the electrons do not collide with gas molecules which could result in loss of energy.
6. E = QV = hf ✔½
  1.6 x 10¹⁹ x 1,200 = 6.63 x 10³⁴ x f ✔½
  f = 2.9 x 1018 Hz ✔