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Physics
WAEC / WASSCE 2017
Atomic, Quantum, Nuclear Physics & Electronics
Solution
Which of the following devices converts light energy to electrical energy?
A
Bulb
B
Television
C
Solar cell
D
Light emitting diode (LED)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The solar cell converts light from the sun to electricity.
Source: Myschool Past Questions Archive (Record #49977)
Physics
WAEC / WASSCE 2017
Work, Energy, Power & Simple Machines
A motor of a corn mill machine operates on electrical energy of \(1.44 \times 10^{5}\)J. If one-quarter of the energy is wasted on sound and heat, determine the efficiency of the machine.
A
25%
B
36%
C
64%
D
75%
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #49979)
Physics
WAEC / WASSCE 2017
Calorimetry, Latent Heat & Change of State
Solution
Thermal energy added or removed from a substance that changes the state of the substance is called
A
latent heat
B
heat of reaction
C
calorimetry
D
specific heat
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Latent heat is thermal energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process.
Source: Myschool Past Questions Archive (Record #49981)
Physics
WAEC / WASSCE 2017
Equilibrium of Forces, Moments & Flotation
Solution
The maximum density of water occurs at a temperature of
A
0°C
B
4°C
C
37°C
D
273°C
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
This is as a result of the Hydrogen bonding in water. Due to the high Kinetic Energy of water, the hydrogen bonds can't hold for too long but from 4^\circC, there's an increase in the hydrogen bonds hence strenghtening it. From the point of production of more hydrogen bonds, the bonding is no longer easily broken. Generally, these and a few factors based on these cause the density of water to be maximum at 4^\circC.
Source: Myschool Past Questions Archive (Record #49991)
Physics
WAEC / WASSCE 2017
Current Electricity & Electric Circuits
Solution
A vapour whose molecules are in dynamic equilibrium with those of its own liquid is said to be
A
unsaturated
B
gaseous
C
saturated
D
diffused
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
A saturated vapour is one which is in a dynamic equilibrium with its own liquid.
Source: Myschool Past Questions Archive (Record #49993)
Physics
WAEC / WASSCE 2017
Waves, Sound & Vibrations
Diagram
Solution
The diagram above illustrates two waves of equal amplitudes A and frequencies approaching each other. When the two waves meet at a point I midway between them, the vertical displacement of the resulting wave will be
Attached Figure / Diagram
A
0
B
\(\frac{A}{2}\)
C
\(\frac{A}{4}\)
D
\(2A\)
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
This is a type of constructive interference. When two waves of equal amplitude are interfering constructively, the resulting amplitude is twice as large as the amplitude of an individual wave.
= A + A = 2A
Source: Myschool Past Questions Archive (Record #49997)
Physics
WAEC / WASSCE 2017
Waves, Sound & Vibrations
Solution
A rainbow is formed when sunlight is incident on water droplets suspended in the air due to
A
interference
B
refraction
C
dispersion
D
diffraction
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Dispersion occurs when different wavelengths of light are refracted by different amounts as they pass through the water droplets, causing the light to spread out into its constituent colors, thereby creating a rainbow.
Source: Myschool Past Questions Archive (Record #50006)
Physics
WAEC / WASSCE 2017
Waves, Sound & Vibrations
Solution
Which of the following statements about the 3rd overtone of a vibrating air column of an open pipe is correct? It has
A
4 nodes
B
5 nodes
C
3 antinodes
D
4 antinodes
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
The 3rd overtone for an open pipe has 5 antinodes and 4 nodes.
Source: Myschool Past Questions Archive (Record #50010)
Physics
WAEC / WASSCE 2017
Waves, Sound & Vibrations
Solution
Consider the wave equation: \(y = 10sin(x - 50t)\), What does the number 10 represent?
A
Acceleration
B
Speed
C
Amplitude
D
Wavelength
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Comparing the given equation with the wave equation:
\(Asin(kx - \omega t)\), we have that A = 10 which is the amplitude of the wave.
Source: Myschool Past Questions Archive (Record #50012)
Physics
WAEC / WASSCE 2017
Waves, Sound & Vibrations
Solution
Plane waves through a narrow gap emerge as circular waves. This phenomenon is known as
A
interference
B
dispersion
C
refraction
D
diffraction
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Diffraction refers to the various things that occur when a wave encounters an obstacle. This bending of the wave after it passes a small gap is an example of diffraction.
Source: Myschool Past Questions Archive (Record #50015)
Physics
WAEC / WASSCE 2017
Reflection, Refraction & Dispersion of Light
Solution
A ray of light incident at an angle \(\theta\) in a rectangular prism grazes the surface of the prism on emerging from the prism. Determine the value of the angle. [Absolute refractive index of the material of the prism is 1.5]
A
41.8°
B
48.2°
C
60.8°
D
90.0°
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
\(\eta = \frac{1}{sin\theta}\)
\(1.5 = \frac{1}{sin\theta}\)
\(sin\theta = \frac{1}{1.5} = 0.667\)
\(\theta = sin^{-1}(0.667) = 41.835^\circ\)
\(\approxeq 41.8^\circ\)
Source: Myschool Past Questions Archive (Record #50018)
Physics
WAEC / WASSCE 2017
Waves, Sound & Vibrations
Diagram
Solution
The diagram above illustrates a wave setup between two fixed ends 4.0m apart. If the speed of the wave is 1.0\(ms^{-1}\), its wavelength and frequency respectively are
Attached Figure / Diagram
A
1m; 0.25Hz
B
2m; 0.25Hz
C
2m; 0.50Hz
D
4m; 0.50Hz
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
For the 4th harmonic, \(L = 2\lambda\)
\(4m = 2\lambda \implies \lambda = \frac{4m}{2}\)
=\(2m\)
Recall, \(v = f\lambda\)
\(1 = f \times 2 \implies f = \frac{1}{2}\)
= 0.50Hz
Source: Myschool Past Questions Archive (Record #50021)
Physics
WAEC / WASSCE 2017
Reflection, Refraction & Dispersion of Light
Solution
Two plane mirrors are inclined at an angle 20^\circ to each other. Determine the number of images formed when an object is placed between them.
A
17
B
18
C
19
D
20
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
The number of images formed = \(\frac{360}{n}\) where the value gotten is odd
else, = \(\frac{360}{n} -1\).
Solving, we have that \(\frac{360}{20} = 18\)
Hence, the no of images formed is 18 - 1 = 17.
Source: Myschool Past Questions Archive (Record #50022)
Physics
WAEC / WASSCE 2017
Lenses & Optical Instruments
Solution
A converging lens of focal length 10cm forms an erect image three times the size of the real object. Calculate the distance between the image and the object.
A
6.6cm
B
11.1cm
C
13.3cm
D
20.0cm
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Given, image size = 3U
object size = U
focal length = 10cm
lens to object distance = \(\frac{focal length \times object size}{image size}\)
= \(\frac{10 \times u}{3u} = 3.33\)
distance between image and object = 10 + 3.33 = 13.33cm
Source: Myschool Past Questions Archive (Record #50030)
Physics
WAEC / WASSCE 2017
Waves, Sound & Vibrations
Solution
The inverse of the time required for a wave to complete one full cycle is called
A
wavelength
B
period
C
frequency
D
amplitude
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The time required to complete one full cycle is the period; the inverse of the period gives the frequency.
Source: Myschool Past Questions Archive (Record #50033)