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The male vocal chords are between 17 mm and 25 mm in length.

1. Let the time taken for o oscillations = 1 sec. 

2. The time taken for one oscillation = 1/υ sec. 

3. But the time taken for one oscillation is called the time period (T) and the number of oscillations per second is called the frequency (υ).

4. Hence frequency and time period are related as T =1/υ (or) υ = 1/T

The characteristics of a sound wave, which play an important role in describing the nature of a wave are

1. Wavelength (λ) 

2. Amplitude (A) 

3. Frequency (υ) 

4. Wave speed (v)

ortime period is the time taken by a vibrating body to complete one oscillation
time period is represented by the letter T. 
second (s) is the SI unit of time period.

The pitch of voice differs for person to person which in turn depends on frequency. So, the frequency is the characteristic of sound which helps to identify my friends voice.

In musical terms, the pitch of the note determines the position of the note on the musical scale which is denoted as :

The tuning fork set is prepared based on the above frequencies.

1) Imaging of organs : Ultra sonics are useful in Electro Cardio Graphy (ECG) to form an image of heart. 

Ultrasonography is used in the formation of images of organs such as liver, gall bladder, uterus, etc. to identify the abnormalities and tumors. Ultrasonography is also used to monitor the growth of a focus inside the mother’s womb.

2) Surgical use of ultrasound : Ultrasounds are used in cataract removal, breaking up of stones in kidneys, etc. without surgery.

Ultrasound imaging uses sound waves to produce pictures of the inside of the body. It helps diagnose the causes of pain, swelling and infection in the body's internal organs and to examine an unborn child (fetus) in pregnant women. 

Drum produces higher pitch.

(a) Woman has short vocal chords. The male vocal chords are between 17 mm and 25 mm in length whereas of a woman are between 12.5 mm and 17.5 mm long.

(b) Woman produces sound of higher pitch.

a) Mass number of X = 6 + 6 = 12 

Mass number of Y = 6 + 8 = 14 

b) Since X and Y both have atomic numbers as 6 but mass numbers are different. 

∴ These are isotopes to each other.

1) Drilling holes and making cuts of desired shapes : 

a) Holes can also be drilled using ultrasonic vibrations. 

b) Ultrasonic cutting and drilling are very effective for fragile materials like glass, etc.

2) Ultrasonic cleaning : 

a) Ultra sonics help in cleaning the parts located in hard-to-reach places. 

b) The high frequency ultrasonic vibrations knocks off all dirt and grease particles from the objects. 

3) Ultrasonic detection of defects in metals : 

The defects in the metallic structures, which are not visible from the outside, can be detected by ultrasonic waves.

1. Sound is a form of energy which travels through the air and reaches our ears to give the sensation of sound. 

2. There may be two possible ways by which transfer of energy from the source of sound to our ears take place. 

a) Source of sound produces disturbances in air and they strike our ears. 

b) Some particles are shot off from the source of sound and they reach our ears.

3. If the second explanation is correct, the vibrating body would gradually lose its weight as particles are continuously shot off from it. 

4. This is impossible because it would lead to vanishing of the object. 

5. Hence the first explanation that the sound travels through disturbances in the form of waves is correct.

1. Uranium – 235 

2. Cobalt – 60

(Given g = 10 ms^-2 and speed of sound = 340 ms^-1) 

Height = 750m 

h = ut + 0.5 gt² 

The initial velocity is 0 750 = 0.5 × 10 × t² 

t = 10 sec

Speed of sound is 340m/sec 

So, time taken to travel 750m upwards is,

\(\frac{750}{340}\) = 2.20 S

time taken = 10 + 2.20 = 12.2 sec.

Correct Answer is: (b, c)

The speed of sound is less than the speed of light. Due to this, light reaches to us faster than sound. Hence, during lightning we see the streak of light earlier than hearing the sound of thunder.

Correct option is: (D) 2040 m

Application of acoustics in nature:

i. Bats apply the principle of acoustics to locate objects. They emit short ultrasonic pulses of frequency 30 kHz to 150 kHz. The resulting echoes give them information about location of the obstacle. This helps the bats to fly in even in total darkness of caves.

ii. Dolphins navigate underwater with the help of an analogous system. They emit subsonic frequencies which can be about 100 Hz. They can sense an object about 1.4 m or larger.

Frequency is f = \(\frac{No\, of\, Vibrations}{time} = \frac{125}{5} = 25 Hz\)

Time period : 2 s

frequency : 0.5 oscillations/sec

B) time period

B) Hearing to continuous explosive sounds of guns can lead to hearing problems.

Given: v_s = 10 m/s, v = 340 m/s, n₀ = 400 Hz

Apparent frequency (n), velocity of sound (v_s) in each case

Formulae:

i. n = n₀ \((\frac{v}{v-v_s})\)

ii. n = n₀ \(\frac{v}{v+v_s}\)

Calculation:

a. As the train approaches the platform, using formula (i),

n = 400 \((\frac{340}{340-10})\) = 421.12 Hz

b. As the train recedes from the platform, using formula (ii),

n = 400 \((\frac{340}{340+10})\) = 388.57 Hz

ii. The relative motion of source and observer results in the apparent change in the frequency but has no effect on the speed of sound. 

Hence, the speed of sound remains unchanged in both the cases.

(a) Veena 

(b) Flute 

(c) Table 

(d) Cymbals

Correct option is D) Sound has energy

Correct option is B) amplitude

Correct option is C) Child

Correct option is D) vacuum

Correct option is D) Sound

i. Sound wave is a longitudinal wave. 

ii. Sound cannot travel in vacuum. 

iii. 

a. Reverberation is the phenomenon in which sound waves are reflected multiple times causing a single sound to be heard more than once.

b. An echo is the repetition of the original sound because of reflection by some surface.

iv. The characteristic of sound which is determined by the value of frequency is called as the pitch of the sound.

SOUND NAVIGATION AND RANGING.

Some harmful effects of noise pollution are:

1. Lack of sleep 
2. Hypertension 
3. Anxiety 
4. Temporary or even permanent loss of hearing.

Sound can not travel in vacuum.

a) When the air is gradually pumped out of the glass vessel, the ringing of the electric bell cannot be heard as there is a creation of vacuum inside the glass vessel. As there are no air molecules inside the glass jar, sound waves cannot travel. 

b) Sound cannot be heard on the moon because there is no air on the moon which acts as a carrier of sound waves. Astronauts talk to one another with the help of radio waves as these waves can travel through the vacuum.

When the ringing bell is suspended in a vacuum chamber it cannot be heard outside because there are no air molecules that vibrate to carry the sound waves.

Solid: Metal- Iron, Aluminium etc. 

Liquid: Water 

Gas: Air

a) Vibrations in the stretched strings of sitar 

b) Vibrations from the stretched membrane 

c) Vibrations from the prongs 

d) Vibrations from the wings 

e) Vibrations from the air columns

The ringing bicycle bell does not produce sound when it is held tightly with hand because the vibrations are stopped and so the sound production stops.

Vacuum cannot transmit sound because sound needs a material medium to travel.

i. Timbre of a sound refers to the quality of the sound which depends upon the mixture of tones and overtones in the sound. Same sound played on different musical instruments feels significantly different and the musical instrument from which the sound generated can be easily identified.