## PHYSICS SOLUTION

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PHYSICS OBJ
11-20: ECDDCDBCCB
41-50: EDACDCACAA
51-60: CEBACCBCAC

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“`PART I: ANSWER NO.1 AND ANY OTHER 5 QUESTIONS“`

(1a)
(i) Solar Water Heater: A solar water heater is a device that captures solar energy and uses it to heat water. It typically consists of solar collectors (usually mounted on rooftops or other sunny locations) that absorb sunlight and transfer the heat to water, which is then stored in an insulated tank. The heated water can be used for various purposes like bathing, washing, and space heating.

(ii) Solar Air Heater: A solar air heater is a device that captures solar energy and uses it to heat air. It usually consists of a dark-colored, heat-absorbing surface that collects solar radiation and transfers the heat to the passing air. The heated air can be used for space heating in buildings or for other heating purposes.

(1b) (1c)
Total Magnification = Magnification of Objective Lens × Magnification of Eyepiece Lens

Given,
Total Magnification = 10
Magnification of Objective Lens = 2

Let “E” represent the magnification of the eyepiece lens.

10 = 2 × E
E = 10/2
E = 5
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(2a)
Static friction is a type of frictional force that occurs between two surfaces in contact with each other when there is no relative motion between the two surfaces.

(2b)
Coefficient of static friction (μs) = Force of static friction/ Normal force

Give:
Force of static friction = 3N
Normal force = 5N

μs = 3N / 5N = 0.6

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(4a)
The velocity ratio of a machine is the ratio of the distance moved by the effort or input force to the distance moved by the load or output force. It measures the advantage gained in the force or speed when using a machine.

(4b)
(i) In a second order lever the fulcrum is located at one end with the load and effort on opposite sides While in a third order lever, the fulcrum is located at one end but the load is in the middle and the effort is at the other end.
(ii) Second order levers require less effort to move a heavier load whereas a third order lever requires more effort to move the same load.
(iii) In a second order lever the force exerted by the effort is in the same direction as the movement of the load While in a third order lever, the force exerted by the effort is in the opposite direction to the movement of the load.
(iv) In a second order lever the range of motion of the load is larger than the range of motion of the effort While in a third order lever, the range of motion of the effort is larger than the range of motion of the load.
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(7)
Given:

– Angle of incidence (θ₁) = 60°
– Speed of light in air = 3×10⁸ m/s
– Speed of light in glass = 2×10⁸ m/s

The refractive index (n) of a medium can be calculated using the formula:

n = speed of light in vacuum / speed of light in the medium

Refractive index of air (n₁):

n₁ = speed of light in vacuum / speed of light in air

n₁ = 3×10⁸ m/s / 3×10⁸ m/s
n₁ = 1

Refractive index of glass (n₂):

n₂ = speed of light in vacuum / speed of light in glass

n₂ = 3×10⁸ m/s / 2×10⁸ m/s
n₂ = 1.5

Using Snell’s law to find the angle of refraction (θ₂):

n₁ × sin(θ₁) = n₂ × sin(θ₂)

1 × sin(60°) = 1.5 × sin(θ₂)

sin(θ₂) = (1 × sin(60°)) / 1.5
sin(θ₂) = sin(60°) / 1.5
θ₂ = arcsin(sin(60°) / 1.5)

θ₂ ≈ arcsin(0.86602540378 / 1.5)
θ₂ ≈ arcsin(0.57735026919)
θ₂ ≈ 35.26°

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(8a)
(i) They are used in electric motors to convert electrical energy into mechanical energy.
(ii) They are used in speakers and headphones to convert electrical signals into sound waves.

(8b)
The soft iron bar can be converted to a magnet by using magnetic induction. This can be done by placing the bar magnet near one end of the soft iron bar and allowing the magnetic field from the bar magnet to induce magnetism in the soft iron. This can be achieved by repeatedly stroking the bar magnet along the length of the soft iron bar in the same direction. As the magnet is stroked the magnetic domains within the soft iron will align in the same direction creating a magnetic field and converting the soft iron bar into a magnet.
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(9a)
Reactance is the opposition that an electrical circuit presents to the flow of alternating current (AC) due to capacitance or inductance. It is measured in ohms and is represented by the symbol X.

(9b)
The reactance of a capacitor is given by:
Xc = 1/2πfc

Where,
Xc = capacitive reactance
F = frequency
C = Capacitance

Given:
Capacitive reactance (Xc) = 3000Ω
Capacitance (C) = 5µF = 5 * 10-⁶ F
π = 3.14

Solving for frequency;
F= 1/2 *π *Xc *C

F = 1/2 * 3.14 * 3000 * 5 * 10-⁶

F= 10.62Hz

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(10a)
Photoelectrons are electrons that are emitted from a material when it absorbs electromagnetic radiation, such as light. The energy of the absorbed radiation is transferred to the electrons in the material, which causes them to be ejected from the surface.

(10b)
Formula for threshold frequency;
F = E/h

Where,
F= Frequency
E = Work function(Energy)
h= Plank’s constant (6.6×10-³⁴)

Converting the work function to joules:
Work function (ϕ) = 3.5 eV = 3.5 × 1.6 × 10-¹⁹ J = 5.6 × 10-¹⁹ J

Substituting the values
F = E/h

F= 5.6 × 10-¹⁹/6.6×10-³⁴

F= 8.48×10¹⁴Hz
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(11a)
(i) Radiation Exposure: X-rays are a form of ionizing radiation, which means they have enough energy to remove tightly bound electrons from atoms, creating ions. Prolonged or excessive exposure to X-rays can damage living tissues and cells, potentially leading to various health issues, including an increased risk of cancer.

(ii) Acute Radiation Sickness: In cases of high-dose or accidental exposure to X-rays, individuals may experience acute radiation sickness. Symptoms can include nausea, vomiting, diarrhea, weakness, and even life-threatening complications. Acute radiation sickness is a severe condition that requires immediate medical attention.

(11b)
(i) Soft X-rays have lower energy levels between 0.1-10 kilo electron volts while hard X-rays have higher energy levels greater than 10 keV.
(ii) Soft X-rays are absorbed more easily by materials while hard X-rays have greater penetration power.
(iii) Soft X-rays are used in medical imaging while hard X-rays are used in industrial applications.
(iv) Soft X-rays can be produced using low-energy X-ray tubes while hard X-rays require higher-energy sources.

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“`PART II: ANSWER FOUR (4) AND QUESTIONS ONLY“`

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