37 past paper MCQs on Characteristics of a Wave and Wave Speed, from the Waves unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.In a ripple tank 40 waves pass through a certain point in one second. If the wavelength of the waves is 5 cm, then find the speed of the wave. (MDCAT 2020)
Correct answer: (a) $2\ \mathrm{m\,s^{-1}}$
$v=f\lambda=40\times0.05=2\ \mathrm{m\,s^{-1}}$.
2.The product of frequency and time period is equal to: (MDCAT 2020)
Correct answer: (a) 1
$T=1/f$, so $fT=1$.
3.The shortest distance between any two points in phase on a wave is called the: (MDCAT 2022)
Correct answer: (c) wavelength
That distance is one wavelength.
4.Which of the following increases by increasing the amplitude? (MDCAT 2022)
Correct answer: (d) loudness
The energy of a wave goes as the square of the amplitude, and for sound that is heard as loudness.
5.An observer standing near the shore observes 54 waves per minute. If the wavelength of the water wave is 2 m, the speed of the water wave is: (MDCAT 2023)
Correct answer: (d) none of these
$f=54/60=0.9$ Hz and $v=f\lambda=0.9\times2=1.8\ \mathrm{m\,s^{-1}}$, which is none of the first three.
6.Wave trough refers to the: (MDCAT 2023)
Correct answer: (d) lowest point of the wave
The trough is the lowest point of a transverse wave, as the crest is the highest.
7.When a wave goes from one medium to another, there is no change in the: (MDCAT 2023)
Correct answer: (a) frequency
The source sets the frequency, so it is unchanged; the speed and hence the wavelength change with the medium.
8.In transverse waves the portion above the mean level is called the: (MDCAT 2024)
Correct answer: (b) wave crest
The high point of a transverse wave is a crest; the low point is a trough.
9.The distance between two successive particles which are exactly in the same state of vibration is called: (MDCAT 2024)
Correct answer: (c) wavelength
Particles one wavelength apart are in phase, which is what the same state of vibration means.
10.A source of sound moves towards a stationary observer with a speed one third that of sound. If the frequency of the source is \$100\,\mathrm{Hz}\$, the apparent frequency heard by the observer is: (UHS MDCAT 2017)
Correct answer: (d) $150\,\mathrm{Hz}$
$f^{\prime}=\dfrac{vf}{v-u}=\dfrac{100v}{v-v/3}=\dfrac{3}{2}\times100=150\,\mathrm{Hz}$.
11.A source of frequency \$f\$ moves with a velocity \$u\$ towards a stationary listener. If \$v\$ is the speed of sound, the apparent frequency heard is: (UHS MDCAT 2017)
Correct answer: (c) $\dfrac{vf}{v-u}$
An approaching source shortens the wavelength, so the speed of sound is divided by $v-u$ and the pitch rises.
12.A wave has velocity 300m/s and frequency 100Hz. If the medium is changed so that velocity doubles but frequency remains constant, the new wavelength will be: (KMU MDCAT 2025)
Correct answer: (b) Doubled
With the frequency fixed, $\lambda=v/f$ doubles when the speed doubles.
13.If 20 waves pass a point in 2 seconds and with a speed of 5m/s, then the wavelength of wave is: (SZABMU MDCAT 2025)
Correct answer: (a) 0.5 m
Twenty waves in two seconds is $10\,\mathrm{Hz}$, and $\lambda=v/f=5/10$ is $0.5\,\mathrm{m}$.
14.A longitudinal wave has a frequency of 500 Hz and wavelength of 0.6 m, its speed is: (SZABMU MDCAT 2025)
Correct answer: (c) 300 m/s
$v=f\lambda=500\times0.6$, which is $300\,\mathrm{m\,s^{-1}}$.
15.In transverse waves the portion above the mean level is called: (UHS MDCAT 2024)
Correct answer: (b) Wave crest
The rise above the undisturbed level is a crest; the dip below it is a trough.
16.The distance between two successive particles which are exactly in the same state of vibration is called (UHS MDCAT 2024)
Correct answer: (c) Wavelength
The distance between two particles in the same phase is one wavelength.
17.Normal person hears 20Hz to 20KHz. Maximum wavelength is: (NUMS MDCAT 2024)
Correct answer: (a) 17m
The longest wavelength goes with the lowest frequency, $340/20$, that is about $17\,\mathrm{m}$.
18.Which of the following increase by increasing amplitude? (UHS MDCAT 2023)
Correct answer: (d) Loudness
Loudness follows the energy of the wave, which goes as the square of the amplitude.
19.The shortest distance between any two points in phase on a wave is called: (UHS MDCAT 2023)
Correct answer: (c) Wavelength
The shortest distance between two points in the same phase is the wavelength.
20.Wavelength of wave is defined as: (SZABMU MDCAT 2023)
Correct answer: (a) Distance between two consecutive crests
One wavelength is the distance from one crest to the next.
21.Maximum displacement of particles form it mean position is called: (SZABMU MDCAT 2023)
Correct answer: (b) Amplitude
The greatest displacement from the mean position is the amplitude.
22.The ultrasonic waves have frequency higher than: (SZABMU MDCAT 2023)
Correct answer: (b) 20 KHz
Ultrasonic means above the upper limit of hearing, about $20\,\mathrm{kHz}$.
23.The maximum displacement of particles of a medium, on either side of the mean position of a wave, is called: (NUMS MDCAT 2023)
Correct answer: (c) Amplitude
That greatest displacement is the amplitude.
24.When a wave goes from one medium to another, there is a no change in the: (UHS MDCAT 2023)
Correct answer: (a) Frequency
The source sets the frequency, so it is unchanged; the speed and wavelength alter together.
25.An observer standing near the sea shore observes 54 waves per minute. If the wavelength of the water wave is 10m then the velocity of water wave is: (UHS MDCAT 2023)
Correct answer: (b) 9 m/s
Fifty-four waves a minute is $0.9\,\mathrm{Hz}$, and $v=f\lambda=0.9\times10$ is $9\,\mathrm{m\,s^{-1}}$.
26.Pitch is ___ proportional to frequency. (PMC MDCAT 2022)
Correct answer: (a) Directly
The higher the frequency the higher the pitch.
27.The property of musical sound which differentiate between grave and shrill sound is called? (PMC MDCAT 2022)
Correct answer: (a) Pitch
A grave note is low and a shrill one high, so the difference is one of pitch.
28.Pitch depends upon: (PMC MDCAT 2022)
Correct answer: (a) Frequency
The higher the frequency the higher the pitch.
29.Unit of frequency is: (PMC MDCAT 2022)
Correct answer: (a) Hertz
Frequency is measured in hertz, one cycle a second.
30.The horizontal distance travelled by wave during one complete cycle is called (NUMS MDCAT 2022)
Correct answer: (b) Wavelength
The distance covered in one complete cycle is the wavelength.
31.Loudness of the sound is directly rotated to: (NUMS MDCAT 2022)
Correct answer: (a) Intensity of sound
Loudness follows the intensity, which is the energy carried each second through unit area.
32.The phase angle between two points is 3π. The distance between these points is 15 cm. What is the wavelength of the wave? (PMC Practice 2021)
Correct answer: (d) 10 cm
A phase of $2\pi$ is one wavelength, so $3\pi$ is $1.5\lambda$, and $15/1.5$ is $10\,\mathrm{cm}$.
33.The shortest distance between two points on the wave that have a phase difference of (π/3) is 5 cm. What is its wavelength? (PMC Practice 2021)
Correct answer: (c) 30 cm
A phase of $2\pi$ is one wavelength, so $\pi/3$ is $\lambda/6$, and $6\times5$ is $30\,\mathrm{cm}$.
34.In a periodic wave, the distance between the second and fifth crest is 15 cm. What is the wavelength of the wave? (PMC Practice 2021)
Correct answer: (b) 5 cm
From the second crest to the fifth is three wavelengths, so $\lambda$ is $5\,\mathrm{cm}$.
35.In a ripple tank, 40 waves pass through a certain point in 1 second. If the wavelength of the wave is 5 cm, then speed of the wave is: (PMC MDCAT 2020)
Correct answer: (d) 2 ms-1
$v=f\lambda=40\times0.05$, that is $2\,\mathrm{m\,s^{-1}}$.
36.If the time period of the oscillation is 20 micro-sec, then what will be the frequency of that oscillating body? (UHS MDCAT 2018)
Correct answer: (b) 50000 Hz
$f=1/T=1/(20\times10^{-6})$, that is $5\times10^4\,\mathrm{Hz}$.
37.Frequency audible range to human hearing lies in the range: (UHS MDCAT 2016)
Correct answer: (c) 20-20000 Hz
The human ear hears from about $20\,\mathrm{Hz}$ to $20\,\mathrm{kHz}$.