Physics Paper 2 Questions and Answers - Samia Joint Mock Examination 2023

INSTRUCTIONS TO CANDIDATES

This paper consists of two Sections A and B.
Answer all questions in Section A and B in the spaces provided.
All working must be clearly shown in the spaces provided
Mathematical tables and electronic calculators may be used.

Section A: (25 MARKS)

The figure below shows an electromagnet. State the polarities at X and Y. (1 mark)
A boy watching fireworks display sees the light from an explosion and hears the sound 2.5 seconds later. Determine how far the explosion is. (Speed of sound in air 330m/s (3 marks)
The figure below shows a ray of light incident to a mirror and striking it at an angle of incidence, 45°. The two mirrors are inclined at an angle of 45°.

Complete the path of the path followed by the ray after reflection until the ray leaves the region. between the two inclined mirrors. (2 marks)
The figure below shows a conductor carrying current placed in the magnetic field and moves in the direction shown.

Identify the polarities of X ad Y (1 marks)
State one defect of a simple cell and explain how it can be minimized. (2 marks)
Gamma, radio waves, green, infrared, X-rays are part of the electromagnetic spectrum.
1. Arrange these radiations in order of increasing energy. (1 mark)
2. State how radio waves are detected. (1 mark)
The figure shows a vertical object, O, placed in front of a convex mirror.

On the same diagram draw the appropriate rays and locate the image formed. (2 marks)
A heater is marked 3kW, 240V. The fuses available are marked 10A, 13A and 20A. Which fuse is most suitable? (3 marks)
A water wave whose wavelength is 7.5cm in the deep end of an inclined tank has a wavelength of 3.0cm in a shallow end. If the speed of the wave in the shallow end is 0.6m/s, calculate its speed in the deep end. (3 marks)
A lens forms a clear image on a screen when the distance between the screen and the object is 100cm. If the image is 4 times the height of the object, determine;
1. The distance of the image from the lens. (2 marks)
2. The focal length of the lens (2 marks)
State two factors that affect the strength of an electromagnet. (2 marks)

SECTION B: (55 MARKS)

Answer all questions in the spaces provided.

Waves are produced in a ripple tank. The following is an example of the wave from what was observed
1. Determine the frequency of the wave. (2 mark)
2. Ultrasound scanning can be used by doctors to obtain information about internal structure of human body without the need of surgery. Pulses of ultrasound area sent into the body from the transmitter placed on the skin.
  1. The ultrasound used has a frequency of 4.5MHz. State why waves of this frequency are called ultrasound. (1 mark)
  2. A pulse of ultrasound enters the body and its reflection returns to the transmitter after a total time of 1.6 x 10⁻⁴s. Calculate how far the reflecting surface is given that the average speed of ultrasound in a body = 1600m⁻¹
3. In an experiment to observe interference of light waves, a double slit was placed close to the source as shown in the figure below.
  1. Define a monochromatic source. (1 mark)
  2. State the function of the double slit. (1 mark)
  3. Briefly describe what is observed on the screen (2 marks)
  4. Briefly explain what is observed on the screen when;
    1. The separation S1 S2 is reduced. (1 mark)
    2. White light source is used in place of monochromatic source. (1 mark)
1. State one condition necessary for total internal reflection to occur. (1 mark)
2. The figure below shows a ray of light incident on the boundary between two media 1 and 2 at an angle θ
  
  Show that the refractive index for a ray of light travelling from medium 1 and medium 2 is given by η = ¹/_Sin θ(3 marks)
3. The figure below shows a ray of light incidence on one face of a block of ice of refractive index
  1.31 and totally reflected at the adjacent face.
  
  Determine: -
  1. Angle Φ (2 marks)
  2. Angle → (2 marks)
1. The figure below shows a human eye with a certain defect. A near object O is placed in front of the eye.
  1. Name the defect (1 mark)
  2. State one cause of the defect. (1 mark)
  3. Illustrate on the same diagram how to defect is corrected. (2 marks)
2. In an experiment to determine the focal length of a converging lens, a group of form four students collected some data and used the results to plot the graph shown in the figure below
  
  Using the graph above, determine: -
  1. The object position when the image position is 45cm. (2 marks)
  2. Slope of the graph (2 marks)
  3. The focal length of the lens given m = ^v/_f − 1, hence the power of the lens. (3 marks)
1. State Ohm's law (1 mark)
2. The figure below shows a circuit with a coil used to warm oil in a beaker.
  1. Explain how heat is produced in the coil. (2 marks)
  2. Given that the reading of the ammeter is 2.4A, determine the resistance of the coil. (2 marks)
  3. How much heat is produced in coil in a minute? (3 marks)
  4. Give two changes that can be made in the set up in order to produce more heat per minute. (2 marks)
  5. A wire of diameter of 0.64mm, length 64.3cm and allows a current of 3.0A. A p.d 6V is maintained at its ends. Calculate its resistivity.
    (2 marks)
1. State the basic law of electrostatics. (1 mark)
2. The figure below shows a sharp pin fixed on a cap of leaf electroscope. The electroscope is highly charged and then left for some time.
  
  Explain why the leaf collapses. (2 marks)
3. The figure below shows a pair of parallel plates of capacitors connected to a battery. The upper plate is displaced slightly to the left.
  
  Suggest two adjustments that can be made so as to increase the effective capacitance.
4. The figure shows 1uF, 2uF, 4uF and 5uF capacitors connected to a battery. (2 marks)
  
  Determine: -
  1. The total capacitance. (2 marks)
  2. The total charge. (2 marks)
  3. Voltage across the 3uF capacitor (3 marks)

MARKING SCHEME

SECTION A (25marks)

The figure below shows an electromagnet. State the polarities at X and Y. (1mark)
- X - South
- Y - South
A boy watching fireworks display sees the light from an explosion and hears the sound 2.5seconds later. Determine how far the explosion is. (Speed of sound in air 330m/s). (3marks)
D = s.xt
= 3.30.X.2.5.
= 825.m.
The figure below shows a ray of light incident to a mirror and striking it at an angle of incidence, 45°.The two mirrors are inclined at an angle of 45°

Complete the path of the path followed by the ray after reflection until the leaves the region between the two inclined mirrors. (2marks)
Figure below shows a conductor carrying current placed in the magnetic direction shown field and moves in the direction shown
Identify the polarities of X and Y. (1mark)
X - North
Y - South
State one defect of a simple cell and explain how it can be minimized. (2marks)
- Polarization - Adding depolariser manganese (iv) oxide
- Local action - Amalgamation by mercury ( use of pure zinc.)
Gamma, radio waves, green, infrared, x-rays are part of the electromagnetic spectrum.
1. Arrange these radiations in order of increasing energy (1mark)
  - Radio, IR, Green, x-rays, Gamma
    * Arrow can be used to show this
2. State how radio waves are detected (1mark)
  - By resonant Circus in radio receivers with diodes and earphones.
The figure shows a vertical object, O, placed in front of a convex mirror.

On the same diagram draw the appropriate rays and locate the image formed. (2marks)
A heater is marked 3kW, 240V. The fuses available are marked 10A, 13A and 20A. Which fuse is most suitable? (3 marks)
I = ^Q/_V = ³⁰⁰⁰/₂₄₀ = 12.5A
Suitable fuse is 13A
A water wave whose wavelength is 7.5cm in the deep end of an inclined tank has a wavelength of 3.0cm in a shallow end. If the speed of the wave in the shallow end is 0.6m/s, calculate its speed in the deep end. (3marks)
f = ^V/_Λ =^0.6/_0.03= 20Hz
V = FΛ
= 20 x 0.075
= 1.5m/s
A lens forms a clear image on a screen when the distance between the screen and the object is 100cm. If the image is 4 times the height of the object, determine;
1. The distance of the image from the lens. (2 marks)
  M = 4
  M = ^V/_U V = m x u
  = 4 x 100 = 400cm
2. The focal length of the lens. (2marks)
  m = V/f − 1 1/f = 1/u + 1/v
  5 = ⁴⁰⁰/_f or 1 = 4 + 1 = 5
  f = 80cm f 400 400
  f = 80 cm
State two factors that affect the strength of an electromagnet.
- Number of turns on the coil
- Nature of the coil
- Amount of current flowing in the coil

SECTION B (55marks)

Waves are produced in a ripple tank. The following is an example of the wave from that was observed.
1. Determine the frequency of the wave. (2 marks)
  f = 1/T
  = ½
  1. = 0.5Hz
2. Ultrasound scanning can be used by doctors to obtain information about internal structure of human body without the need of surgery. Pulses of ultrasound are sent into the body from the transmitter placed on the skin.
  1. The ultrasound used has a frequency of 4.5MHz. State why waves of this frequency are called ultrasound. (1 mark)
    - Are waves of very high frequency or Are waves of very shorter wavelength
  2. A pulse of ultrasound enters the body and its reflection returns to the transmitter after a total time of 1.6×10⁻⁴S. Calculate how far the reflecting surface is given that the average speed of ultrasound in a body = 1500ms⁻¹(3 marks)
    D = S x T
    2
    = 1500 X 1.6 X10⁻⁴ 2
    = 0.12M
  3. In an experiment to observe interference of light waves a double slit placed close to the source as shown in figure below
    1. Define a monochromatic source. (1 mark)
      - A source of same frequency
    2. State the function of the double slit. (1 mark)
      - To produce cuherent sources of light.
    3. Briefly describe what is observed on the screen (2 marks)
      - Alternating dark and bright fringes due to alternating destructive and constructive interference.
    4. Briefly explain what is observed on the screen when: -
      1. The separation S1 S2 is reduced. (1 mark)
        
        Fringe / seperation distance increases
      2. White light source is used in place of monochromatic source.
        
        Bright fringe for consmutive interference and band of 7 colours for destructive interference (1 mark)
1. State one condition necessary for total number of internal reflection to occur. (1mark)
  - Angle of incidence must exceed critical angle
  - Ray must travel from opticully denser medium to optically less dense medium
2. The figure below shows a ray of light incident on the boundary between two media 1 and 2 at an angle θ.
  Show that the refractive index for a ray of light travelling from medium 1 and medium 2 is given by n = 1/sin θ
  n₂ = Sin 90°
  Sin θ
  but sin 90° = 1
  n₂ = ¹/_Sinθ
3. The figure below shows a ray of light incidence on one face of a block of ice of refractive index 1.31 and totally reflected at the adjacent face.
  Determine:
  1. Angle Φ (2 marks)
    n = ¹/_Sinθ
    1.31 = ¹/_Sinθ
    θ° = Sin⁻¹ (¹/_1.31)
    = 49.76°
  2. Angle θ (2 marks)
    1.31 = Sin θ
    40.24
    Sin θ 1.31 Sin 40.24
    θ = Sin⁻¹ (0.8462)
    = 57·81°
1. The figure below shows a human eye with a certain defect. A near object O is placed in front of the eye.
  1. Name the defect. (1mark)
    - long sightedness
  2. State one cause of the defect (1mark)
    - Eye ball too small
    - Eye Teas too long.
  3. Illustrate on the same diagram how the defect is corrected. (2marks)
2. In an experiment to determine the focal length of a converging lens, a group of form four students collected some data and used the results to plot the graph shown in figure below.
  
  Using the graph above, determine:
  1. The object position when the image position is 45 cm (2marks)
    v = 45
    m = 3.2
    u = m x v
    m = ^V/_U
    m = 45
    3.2
    = 14.0625 cm
  2. Slope of the graph. (2marks)
    DM = 3 − 0
    DV = 42 − 10
    = 3/22
    = 0.09375
  3. The focal length of the lens given m = v/f −1, hence the power of the lens. (3marks)
    f = 1/slope
    =¹/_0.09375
    = 10.67cm
    p = ¹/0_.1067
    = + 9.375D
1. State Ohm's law (1mark)
  - Current flowing through conductor is directly proportional to potential difference across conductor provided other physical conditions are kept constant.
2. The figure below shows a circuit with a coil used to warm oil in a beaker.
  1. Explain how heat is produced in the coil. (2 marks)
    - Currents flows in the heater coil after ashort circuiting V, resistance of the coil produces the heating effect.
  2. Given that the reading of the ammeter is 2.4A, determine the resistance of the coil (2marks)
    V = IR
    R = V
    R
    = 12
    2.4 = 5.0 Ω
  3. How much heat is produced in coil in a minute? (3marks)
    VIT = 12 x 2.4 x 60
    = 1728
  4. Give two changes that can be made in the set up in order to produce more heat per minute. (2 marks)
    - Increasing the number of cells/ current flowing Howing
    - Increasing the length of the coil
  5. A wire of diameter of 0.64mm, length 64.3 cm and allows a current of 3.0 A. A p.d 6V is maintained at its ends. Calculate its resistivity
    (2 marks)
    Resistivity = R x L
    A
    = V x L
    I x A
    = 6 x 0.643
    3 x 0.00064
1. State the basic law of electrostatics. (1mark)
  - Like charges repel unlike charges
2. The figure below shows a sharp pin fixed on a cap of leaf electroscope. The electroscope is highly charged and then left for some time.
  Explain why the leaf collapses. (2 marks)
  - Charges Concentrate at the sharp point.
3. The figure below shows a pair of parallel plates of capacitors connected to a battery. The upper plate is displaced slightly to the left.
  Suggest two adjustments that can be made so as to increase the effective capacitance. (2 marks)
  - Reduce distance (d)
  - move the upper plate to the right to Increase area of overlap/increase area of overlap.
  - Replace the material between the plates
  - Use of dielectric material
4. The figure shows IuF, 2uF, 4uF and 5uF capacitors connected to a battery.
  Determine:
  1. The total capacitance. (2marks)
    5 x (4 + 1) + 2
    5 + (4 + 1)
    = 4.5μF
  2. The total charge. (2marks)
    Q = CV
    = 4.5 x 10⁻⁶ x 3.0
    = 13.5 x 10⁻⁶C or
    1.35 x 10⁻⁵C
  3. Voltage across the 4uF capacitor. (3marks)
    Q = CV
    = 2.0 x 10⁻⁶ x 3 = 6.0 x 10⁻⁶
    = (13.5 − 6) X 10⁻⁶ = 7.5 X 10⁻⁶
    V = ^Q/_C = 7.5 x 10⁻⁶
    5 x 10⁻⁶
    = 1.5V
    3.0 − 1.5 = 1.5V