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Physics
WAEC / WASSCE 1998
Waves and Optics
The phenomenon which occurs when light changes direction as it passes from one medium to another is called
A
reflection
B
polarisation
C
interference
D
diffraction
E
refraction
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option E.
Source: Myschool Past Questions Archive (Record #33601)
Physics
WAEC / WASSCE 1998
Waves and Optics
What is the image distance of an object placed at a distance of 2f from a converging lens of focal length f?
A
f/4
B
f/2
C
f
D
2f
E
4f
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 #33602)
Physics
WAEC / WASSCE 1998
Waves and Optics
The images formed by diverging lenses are always
A
diminished, virtual and inverted
B
diminished, virtual and errect
C
diminished inverted and real
D
magnidied, virtual and errect
E
magnified, real and inverted
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #33603)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
A converging lens of focal length 5cm is used as a magnifying glass by a man whose nearpoint is 35cm. Calculate the magnification given by the lens
A
8
B
7
C
6
D
5
E
4
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
\(\frac{1}{f} = \frac{1}{u} + \frac{1}{v}\)
= \(\frac{1}{5} - \frac{1}{35} = \frac{30}{175}\)
U = \(\frac{175}{30}\) = 5.8m
\(\frac{v}{u} = \frac{35}{5.8}\)
= 6
Source: Myschool Past Questions Archive (Record #33633)
Physics
WAEC / WASSCE 1998
Waves and Optics
An astronomical telescope having an objective of focal length 100cm and an eyepiece of focal length 10cm is used in normal adjustment, calculate the separation of the lenses
A
0.10m
B
0.90cm
C
1.10m
D
1.80m
E
2.20m
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #33636)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
A lantern gives an image of 3m square of a slide 7.62cm square on a screen. If the screen is 10m from the projection lens of the lantern, calculate the focal length of the lens
A
40.3cm
B
26.1cm
C
24.8cm
D
0.7cm
E
0.3cm
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
M = \(\frac{V_H}{U_H} = \frac{300}{7.62}\)
= 39.3
U = \(\frac{V}{M} = \frac{1000}{39.3}\) = 25.44
\(\frac{1}{f} = \frac{I}{U} + \frac{I}{V} = \frac{I}{25.44} = \frac{I}{1000} = \frac{1025.44}{25440}\)
f = \(\frac{25440}{1025.44} = 24.8\)
Source: Myschool Past Questions Archive (Record #33638)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
The intensity of light falling on the film in a camera depend on the i. brightness of the object. ii. diameter of the aperture stop. iii. speed of the shutter. Which of the statements is/are correct/
A
i, ii and iii
B
i and iii only
C
i and ii only
D
ii and iii only
E
iii only
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
iii. Speed of the shutter: This directly controls how long the film is exposed to the incoming light. A faster shutter speed reduces the time light falls on the film, thereby reducing the intensity (light per unit time) effectively recorded.
Source: Myschool Past Questions Archive (Record #33640)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
the shortest length of the air column in a resonance tube at resonance is 0.12m and the next resonance length is 0.37m. calculate the frequency of vibration given that the speed of sound in air is 340m-1
A
1360Hz
B
694Hz
C
680Hz
D
34Hz
E
340Hz
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
f = \(\frac{v}{2(l_2 - l_1)} = \frac{340}{2(0.37 - 0.12)} = \frac{34}{0.5}\) = 680
Source: Myschool Past Questions Archive (Record #33645)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
A sonometer wire under a tension of N10N, produces a frequency of 250Hz when plucked. Keeping the length of the wire constant, the tension is adjusted to produce a new frequency of 350Hz. Calculate the new tension
A
39.2N
B
19.6N
C
14.2N
D
7.4N
E
5.1N
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
f \(\alpha\) \(\sqrt{T}\)
\(\frac{f_1}{f_2} = \sqrt{\frac{T_1}{T_2}}\)
\(\frac{250}{350} = \sqrt{\frac{10}{T_2}}\)
\(\frac{5}{7} = \sqrt{\frac{10}{T_2}}\)
\(\frac{25}{49} = \frac{10}{T_2}\)
T2 = \(\frac{49 \times 10}{25} = 19.6\)
Source: Myschool Past Questions Archive (Record #33651)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
Calculate he wavelength of a note which is one octave lower than a note of 256Hz in a medium in which the speed of sound is 352ms-1
A
0.69m
B
1.38m
C
2.75m
D
5.50m
E
9.30m
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
\(\lambda\) = \(\frac{v}{f} = \frac{352}{256}\)
= 1.38
Source: Myschool Past Questions Archive (Record #33657)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
An electromagnetic wave of frequency 5.0 x 1014Hz, is incident on the surface of water of refractive index \(\frac{4}{3}\). Taking the speed of the wave in air as 3.0 x 108ms-1, calculate the wavelength of the wave in water.
A
2.2 x 10-6m
B
1.7 x 10-7m
C
8.0 x 10-7m
D
6.0 x 10-7m
E
4.5 x 10-7m
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
\(_an_w = \frac{\lambda_a}{\lambda_w}\)
\(\frac{4}{3} = \frac{\lambda_a}{\lambda}\)
\(\lambda_w = \frac{v}{f}\)
= \(\frac{3.0 \times 10^8}{5.0 \times 10^{14}} = 0.6 \times 10^{-6}\)
\(\lambda_w = \frac{3}{4} \lambda_a = \frac{3}{4} \times 0.6 \times 10^{-6}\)
= 4.5 x 10-7m
Source: Myschool Past Questions Archive (Record #33666)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
When light from a source is sent through a gas
I. Certain wavelengths are absorbed.
II. an emission line spectrum results.
III. A dark line is left.
Which of the following is/are correct?
A
i only
B
iii only
C
i and ii only
D
i and iii only
E
ii and iii only
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
When light from a source is sent through a gas some light of certain wavelengths is absorbed resulting in gaps that appear as dark lines
Source: Myschool Past Questions Archive (Record #33695)
Physics
UTME / JAMB 1998
Waves and Optics
Diagram
Solution
In the AC circuit diagram above, the resonance frequency is
Attached Figure / Diagram
A
5000π Hz
B
2500π Hz
C
5000/π Hz
D
2500/π Hz
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
resonance frequency \(f_r\) = \(\frac{ 1}{ 2\pi \sqrt{LC}}\)
\(f_r\) = \(\frac{1}{2\pi \sqrt{5\times10^{-6} \times 8\times 10^{-3}}}\)
\(f_r\) = \(\frac{1}{ \pi 0.0004}\)
\(f_r\) = \(\frac{ 2500}{\pi}\)
Source: Myschool Past Questions Archive (Record #41745)
Physics
WAEC / WASSCE 1998
Waves and Optics
Solution
Trace the outline PQRS of the glass block on a sheet of paper, as shown in the diagram. Remove the block Mark a position 0 very close to P. Draw the normal NOG From point G, measure and mark out Points \(B_1\) \(B_2\) \(B_3\) \(B_4\) and \(B_5\) along with line GR at distances 1, 2, 3, 4 and 5cm respectively from G. Replace the glass block on the outline PORS Erect a pin at 0 and another at \(B_1\). Now fx a pin at \(T_1\) such that the pins at \(T_1\) and \(B_1\) are in line with the pin at O when viewed through the side SR of the glass block. Remove the glass block. Join the line O\(B_1\) and \(B_1\)\(T_1\). Measure and record the angles x and y. Evaluate sin x and y. Repeat the experiment with the pin at \(B_1\) fixed at \(B_2\), \(B_3\), \(B_4\) and \(B_5\) respectively while the pin at O remains unaltered. In each case, measure and record the values of x, y, sin x, and cos y. Tabulate your readings. Plot a graph of sin x on the vertical axis and cos y on the horizontal.axis, starting both axes from the origin (0,0). Calculate the slope, s of the graph. Evaluate K= \(\frac{1}{s}\). State two precautions taken to ensure accurate results. [Attach your tracings to your answer booklet]
(b)i. State Snell's law of refraction and explain why reaction Occurs at the boundary between two media.
ii. Differentiate refraction from diffraction.
iii. State two conditions necessary for total internal reflection to occur in a medium.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
Table of values/observation
S/N
X^\circ(degree)
y^\circ (degree)
Sin x
Cos y
1
10.00
74.00
0.1736
0.2756
2
20.00
61.50
0.3420
0.4772
3
27.50
47.00
0.4617
0.6820
4
34.00
33.5
0.5592
0.8339
5
40.00
26.00
0.6428
0.8988
6
44.00
14.00
0.6947
0.9703
Slope (s) = \(\frac{\bigtriangleup {\text {sin x}}}{\bigtriangleup {\text {cos y}}} = \frac{0.69-0.03}{0.97-0.1}\)
= \(\frac{0.66}{0.87}\) = 0.7586 = 0.76
K = \(\frac{1}{S} = \frac{1}{0.7586}\) = 1.318 \(\approx\) 1.32
Precautions:
I ensured that the optical pins were vertical
l ensured reasonable spacing of pins.
I used a sharp pencil.
l avoided parallax error in reading the protractor.
(b)i. \(\frac{\text {sin i}}{\text {sin r}}\) = constant for a given pair of media where
i = angle sin r of incidence and
r = angle of retraction.
(ii) Retraction is the bending of rays at the interface of two media while diffraction is the spreading out of rays of light around the edges of obstacles or aperture.
(iii)(1) Light must travel from a dense medium to a less dense medium.
(2) The angle of incidence in the dense medium must be greater than the critical angle.
Source: Myschool Past Questions Archive (Record #60144)
Physics
WAEC / WASSCE 1997
Waves and Optics
Solution
When white light is incident on a glass prism the spectrum produced on a screen placed beyond the prism is due to?
A
Diffraction
B
Reflection
C
Refraction
D
Polarisation
E
Interference
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
White light splits into a spectrum when it passes through a glass prism due to refraction, as different wavelengths bend by varying amounts, causing dispersion.
Source: Myschool Past Questions Archive (Record #26298)