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Physics
UTME / JAMB 1987
Waves and Optics
Solution
A ray of light is incident at an angle of 30o on one top surface of a parallel-sided glass block of refractive index 1.5. The ray finally emerges from the lower surface. What is the angular deviation of the emergent ray?
A
60o
B
39o
C
28o
D
0o
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
To find the angular deviation of a ray of light passing through a parallel-sided glass block, follow these steps:
Calculate the angle of refraction at the first surface: Using Snell's Law:
\(n_1 \sin(\theta_1) = n_2 \sin(\theta_2)\)
where:
\(n_1 = 1 \quad (\text{air}), \quad \theta_1 = 30^\circ, \quad n_2 = 1.5 \quad (\text{glass})\)
Substituting the values:
\(1 \cdot \sin(30^\circ) = 1.5 \cdot \sin(\theta_2) \Rightarrow 0.5 = 1.5 \cdot \sin(\theta_2) \Rightarrow \sin(\theta_2) = \frac{1}{3}\)
Thus,
\(\theta_2 \approx \arcsin\left(\frac{1}{3}\right) \approx 19.47^\circ\)
Angle of incidence at the second surface: Since the block is parallel-sided, the angle of incidence is: \(\theta_3 = \theta_2 \approx 19.47^\circ\)
Calculate the angle of refraction at the second surface: Applying Snell's Law again: \(n_2 \sin(\theta_3) = n_1 \sin(\theta_4)\)
Substituting values: \(1.5 \cdot \sin(19.47^\circ) = 1 \cdot \sin(\theta_4) \Rightarrow \sin(\theta_4) \approx 0.5 \Rightarrow \theta_4 = \arcsin(0.5) = 30^\circ\)
Calculate the angular deviation: The angular deviation \(D\) is given by: \(D = \theta_1 - \theta_4 = 30^\circ - 30^\circ = 0^\circ\)
The angular deviation of the emergent ray is \(0^\circ\).
Source: Myschool Past Questions Archive (Record #28463)
Physics
UTME / JAMB 1987
Waves and Optics
Four lenses are being considered for use as a microscope objective. Which of the following focal lengths is most suitable?
A
-5mm
B
+5mm
C
-5cm
D
+5cm
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 #28464)
Physics
UTME / JAMB 1986
Waves and Optics
A heavy object is suspended from a string and lowered into water so that it is completely submerged. The object appears lighter because
A
the density of water is less than that of the object
B
the pressure is low just below the water surface
C
it experiences an upthrust
D
the tension in the string neutralizes part of the weight
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 #28484)
Physics
UTME / JAMB 1986
Waves and Optics
Which of the following is true of sounds?
A
sound travels faster in air at 20oC than at 30oC
B
the frequency of a given sound wave changes when it crosses the boundary seperating two media
C
the wavelength of a given sound wave in air decreases as the temperature increases
D
sound waves cannot be reflected
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 #28513)
Physics
UTME / JAMB 1986
Waves and Optics
Solution
A lens of focal length 12.0cm forms an upright image three times the size of a real object. The distance between the object and the images is
A
8.0cm
B
16.0cm
C
24.0cm
D
32.0cm
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
an upright image is a virtual image and it is expected to be on the same side as the object for a lens but not for a mirror.
magnification M = \(\frac{v}{u}\) = \(\frac{v}{2}\) = 3 ⇒⇒ v = 3u ( image is virtual = -3u)
using \(\frac{1}{f}\) = \(\frac{1}{u}\) + \(\frac{}{v}\) ⇒⇒ \(\frac{1}{u}\) - \(\frac{1}{3u}\) = \(\frac{1}{12}\)
\(\frac{3 -1}{3u}\) = \(\frac{1}{12}\)
cross multiplying
24 = 3u = u = 8cm but v = 3u = 24cm
virtual image and object are at the side of the lens,
Hence, the distance between the object and the image = 24 - 8 = 16cm.
Source: Myschool Past Questions Archive (Record #28519)
Physics
UTME / JAMB 1986
Waves and Optics
In which of the following arrangements is the wavelength in an increasing order?
A
Gamma rays, infra-red rays, x-rays, radiowaves
B
Gamma rays, x-rays, infra-red ray, radiowaves
C
Radiowaves, x-rays, gamma ray, infra-red rays
D
Infra-red rays, radiowaves, x-rays, gamma rays
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 #28521)
Physics
UTME / JAMB 1986
Waves and Optics
Solution
A dentist obtains a linear magnification of 4 of a hole in a tooth by placing a concave mirror at a distance, of 2.0cm from the tooth. The radius of Curvature of the mirror is
A
5.3cm
B
3.2cm
C
2.7cm
D
1.6cm
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
v = 4u, if u = 2cm, v = 8cm
F = \(\frac{uv}{u + v}\)
= \(\frac{2 \times 8}{2 + 8}\)
= 1.6cm
r = 2F
= 2 x 1.6
= 3.2cm
Source: Myschool Past Questions Archive (Record #28529)
Physics
UTME / JAMB 1986
Waves and Optics
Solution
A pencil is placed vertically between a concave mirror and its focal point. The image of the pencil in the mirror will be
A
real, inverted and diminished
B
virtual, inverted and enlarged
C
real, erect and enlarged
D
virtual, erect and enlarged
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Virtual Image: The image formed is virtual because it cannot be projected on a screen; it appears to be behind the mirror.
Erect: The image is upright relative to the object.
Enlarged: The image is larger than the object when it is placed between the focal point and the mirror.
Source: Myschool Past Questions Archive (Record #28532)
Physics
UTME / JAMB 1986
Waves and Optics
Which of the following is true of the loudness of sound? It
A
depends on the square of the amplitude of the vibrating body
B
is proportional to the distance of the observer from the source of the sound
C
is greatest in vacuum
D
is dependent in vacuum
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #28536)
Physics
UTME / JAMB 1986
Waves and Optics
Solution
A man clapping his hands at regular intervals observes that the echo of a clap coincides with the next clap. If the reflecting cliff is 160m away and the speed of sound is 320ms-1, what is the frequency of the clapping?
A
1 Hz
B
2Hz
C
4Hz
D
8Hz
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Total distance = 2 x 160 = 320cm
Total time = \(\frac{320}{320}\) = 1s
F = \(\frac{1}{1}\) = \(\frac{1}{1}\)
= 1Hz
Source: Myschool Past Questions Archive (Record #28537)
Physics
UTME / JAMB 1986
Waves and Optics
The vibration of an air column produces the sound in the
A
piano
B
guiter
C
flute
D
school handbell
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 #28539)
Physics
UTME / JAMB 1986
Waves and Optics
Diagram
Solution
In fig 6, a ray of light in air strikes a glass plate at an angle of incidence 60 degrees, the reflected ray is observed to be perpendicular to the refracted ray, what is the refractive index of the glass
Attached Figure / Diagram
A
1.73
B
1.50
C
0.87
D
0.57
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
From the diagram above:
refractive index \(_gn_a\) = \(\frac{1}{_an_g}\) = \(\frac{sin r}{sin i}\) = \(\frac{ sin 30}{ sin 60}\) = \(\frac{1}{0.577}\) = 1.732
Source: Myschool Past Questions Archive (Record #41653)
Physics
UTME / JAMB 1985
Waves and Optics
Solution
When a sound wave passes from air into water its
A
speed and frequency increases but its wavelength remains the same
B
speed and wavelength increases but its frequency remains the same
C
speed decreases
D
speed remains the same but its frequency and wavelength change
E
speed increases but its frequency and wavelength decreases
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Speed: The speed of sound is greater in water than in air.
Frequency: The frequency of the sound wave remains constant when it transitions between different mediums.
Wavelength: Since the speed increases while the frequency remains constant, the wavelength must increase as well.
Source: Myschool Past Questions Archive (Record #28622)
Physics
UTME / JAMB 1985
Waves and Optics
Solution
If the fundamental frequency of a closed pipe organ on a day when the speed of sound is 340ms-1 is 170Hz, then the length of the pipe is
A
50cm
B
70cm
C
100cm
D
150cm
E
200cm
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
\(\lambda\) = \(\frac{v}{f}\)
= \(\frac{340}{170}\)
= 2m ; for closed pipe
L = \(\frac{1}{4}\)\(\lambda\)
= \(\frac{1}{4}\) x \(\frac{2}{1}\)
= 0.5m
= 50cm
Source: Myschool Past Questions Archive (Record #28623)
Physics
UTME / JAMB 1985
Waves and Optics
Solution
An object is placed 15cm in front of a concave mirror of radius 40cm. The image formed
A
virtual and 60cm behind the mirror
B
real and 60cm behind the mirror
C
virtual and at infinity
D
real and at infinity
E
virtual and 40cm from the mirror
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
u = f
Source: Myschool Past Questions Archive (Record #28627)