Waves (Physics)

Total Questions: 43

11. When the speed of an object exceeds the speed of sound, it is said to be moving at ________. [S.S.C. Online MTS (T-1) 19.08.2019 (Shift-II)]

Correct Answer: (b) Supersonic motion
Solution:

When the speed of an object exceeds the speed of sound, it is said to be traveling at supersonic speed.

  • The speed of sound in air at standard temperature and pressure is approximately 343 meters per second (about 767 miles per hour).
  • Any object moving faster than this speed is considered supersonic.
  • When an object travels at supersonic speed, it can create shock waves in the air, which can result in a loud "sonic boom" when they reach an observer.

12. Quality of notes in music depends on which factor? [S.S.C. Online Graduation Level (T-I) 2.09.2016 (Shift-II)]

Correct Answer: (c) Harmonic presents
Solution:Quality is that characteristic of a musical sound that enables us to distinguish between the sounds produced by two different musical instruments or two different persons, although their pitch and loudness may be the same.
  • The quality depends primarily on the waveform of the sound.
  • The waveform of the sound emitted by a tuning fork is a simple sine curve.
  • But most bodies vibrate in a very complex manner.
  • Besides the fundamental frequency f, they consist of additional frequencies of 2f, 3f, 4f, etc.
  • These additional tones are called overtones or harmonics.

13. The strength of a wave is proportional to which of the following? [S.S.C. Online Graduation Level (T-I) 7.09.2016 (Shift-II)]

Correct Answer: (c) the square root of the amplitude
Solution:I∝a²
where
a= dimension
I = strength of the wave

Therefore, the strength of a wave is directly proportional to the square of its amplitude.

14. Which of the following determines the pitch of sound? [S.S.C. Online Graduation Level (T-1) 11.08.2017 (Shift-III)]

Correct Answer: (b) Frequency
Solution:

The frequency of the sound wave determines its pitch.

  • Frequency refers to the number of vibrations or cycles of the sound wave that occur per second, measured in Hertz (Hz).
  • High frequency sound waves correspond to high-pitched sounds (like a whistle or a flute).
  • Low frequency sound waves correspond to low-pitched sounds (like a bass drum or a tuba). 
  • While other factors like amplitude (loudness) and timbre (tone color) affect the overall perception of sound, it is primarily the frequency that our ears and brain interpret as the pitch of a sound.

15. What is the number of oscillations per second called? [S.S.C. Online MTS (T-I) 4.10.2017 (Shift-II)]

Correct Answer: (a) Frequency
Solution:

The number of oscillations per second is called frequency.

The unit of frequency is Hertz (Hz), where 1 Hz is equal to one oscillation per second.

16. _______ of a wave is the transfer rate of energy per unit area perpendicular to wave's direction of travel. [S.S.C. Online CHSL (T-1) 24.01.2017 (Shift-I)]

Correct Answer: (c) Intensity
Solution:The intensity of a wave is the rate of transfer of energy per unit area perpendicular to the direction of movement of that wave.

17. Which of the following statements is correct? [S.S.C. Online CGL (T-1) 23.08.2021 (Shift-II)]

Correct Answer: (a) The minimum distance between two points in a wave having the same phase at a particular instant of time is called wavelength.
Solution:Wavelength () of a wave is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
  • It can be defined as the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings.

Therefore option (a) is correct.

18. What is the movement of an object going back and forth called? [S.S.C. Online MTS (T-I) 5.10.2017 (Shift-III)]

Correct Answer: (b) Vibration
Solution:

The movement of an object going back and forth is called oscillation or vibration.

  • These terms are often used interchangeably to describe a repetitive motion around a central equilibrium position.

19. What is the time taken by the pendulum to complete one oscillation? [S.S.C. Online MTS (T-I) 10.10.2017 (Shift-II)]

Correct Answer: (a) Time Period
Solution:The time taken by the pendulum to complete one oscillation is called its time period.

It is usually denoted by the symbol T and its SI unit is second (s).

20. A simple pendulum consists of a small metallic ball or piece of stone suspended from a rigid stand by a thread. The metallic ball is called the ______ of the pendulum. [S.S.C. JE Electrical Exam 22.03.2021 (Shift-I)]

Correct Answer: (b) Bob
Solution:A simple pendulum consists of a small object, called a bob, suspended from a fixed point by a light, inextensible string.

When the bob is displaced from its equilibrium position and released, it swings back and forth under the influence of gravity. This motion is called oscillation.

Motion and Time Class 7 Notes Science Chapter 9 Free PDF