When we say that sound travels in a medium, what do we mean?
In a wave (like sound wave), the particles of the medium, the source nor the medium do not travel. It is the disturbance (energy) which travels along the path.
Which of the following correctly represents the speed of sound in solids, liquids and gases in ascending order?
The speed of sound in ascending order is minimum in gases, lesser in liquid and maximum in solids.
Gas :- 330-340 m/s
Liquid :- 1500 m/s
Solid :- 5000 m/s
A person can hear an approaching train when he presses his ear to the railway track faster than one who simply stands on the tracks. What makes this possible?
The velocity of sound in solids (railway tracks) is faster than that in air.
A person can be identified by his voice. What determines this distinguishing feature?
The characteristics of a sound are :
(i) Loudness or intensity : it distinguishes between a loud or faint sound , and intensity , depends upon amplitude of sound waves .
(ii) Pitch : it distinguishes a sharp sound from a dull sound and pitch depends upon frequency.
(iii) Quality: it distinguishes between sounds generated by two sources .
In human beings, which of the following produces the sound?
Sound is produced by larynx or voice box.
An object oscillates 50 times in one second. What is its frequency?
The number of oscillations per second is called the frequency of oscillation, i.e. 50 Hz.
In which of the three media does sound travel the fastest?
Sound travels the fastest in solids, less in liquids and the least in gases.
Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen. Why?
Thunder is heard later because the speed of light (flash) is much greater (3×108ms−1) than the speed of sound (330ms−1).
What is the cause for the difference in the voices of men, women and children?
Two vocal cords are stretched across the larynx in such a way that it leaves a narrow slit between them for the passage of air. The length of vocal cords and the width of the slit is different in men, women, children, thus producing different sounds.
Which of the following represents Hertz?
Frequency = 1/time period.
= 1/unitof time = second−1
On what factors does the loudness or intensity of sound depend?
The loudness or intensity of sound depends on its amplitude. The larger the amplitude, the louder is the sound produced.
On what factors does the pitch of sound depend?
Pitch of sound depends on its frequency.
Which of the following produces sound in birds?
Birds produce sounds by means of a ring of cartilage called syrinx, present at the beginning of their wind pipe.
Find the difference between a musical sound and noise.
Musical sound is produced by regular vibrations whereas noise is produced by irregular vibrations.
Which of the following are the effects of noise pollution?
(iii) Hearing impairment
Noise pollution is hazardous to health in many ways. Insomnia (lack of sleep), hypertension (high blood pressure) and hearing impairment (temporary or permanent hearing problem) are the effects of noise pollution.
Which of the following frequencies cannot be heard by human beings?
Human beings can hear only within the range of 20 Hz to 20 kHz. So, 100 kHz (1,00,000 Hz) cannot be heard.
Identify the three delicate bones in the middle ear.
The three delicate bones in the middle ear are the hammer, the anvil and the stirrup.
Identify the nerve that carries the signals from the ear to the brain.
The nerve that carries the signals from the ear to the brain is called the auditory nerve.
Which of the following helps human beings in producing sounds?
Vocal cords are a band of muscles within the larynx. These muscles vibrate to produce the sound.
What is the number of vibrations made by a body in one second called?
Frequency is the number of vibrations that pass through a point in space in one second by a body.