Solution:

Sound can travel through

(a) gases only

(b) solids only

(c) liquids only

(d) solids, liquids and gases. CORRECT

Solution:

Voice of which of the following is likely to have minimum frequency?

Solution:

(a) Sound cannot travel in vacuum. (T)

(b) The number of oscillations per second of a vibrating object is called its time period. (F)

(c) If the amplitude of vibration is large, sound is feeble. (F)

(d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T)

(e) The lower the frequency of vibration, the higher is the pitch. (F)

(f) Unwanted or unpleasant sound is termed as music. (F)

(g) Noise pollution may cause partial hearing impairment. (T)

Solution:

(a) Time taken by an object to complete one oscillation is called $Time Period$.

(b) Loudness is determined by the $Amplitude$ of vibration.

(c) The unit of frequency is $Hertz$.

(d) Unwanted sound is called $Noise$.

(e) Shrillness of a sound is determined by the $Frequency$ of vibration.

Solution:

Time Period and Frequency of a Pendulum

The pendulum oscillates 40 times in 4 seconds. We can calculate the time period and frequency using the following formulas:

Frequency (f): The frequency is the number of oscillations per unit time.

Given that the pendulum oscillates 40 times in 4 seconds, the frequency is:

$$f = \frac{\text{Number of oscillations}}{\text{Time}} = \frac{40}{4} = 10 \, \text{Hz}$$

Time Period (T): The time period is the time taken for one complete oscillation. It is the reciprocal of frequency.

$$T = \frac{1}{f} = \frac{1}{10} = 0.1 \, \text{seconds}$$

Solution:

Time Period of Vibration

The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. To find the time period, we use the formula:

Time Period (T) = $ \frac{1}{\text{Frequency (f)}} $

Given: Frequency (f) = 500 vibrations per second

So, Time Period (T) = $ \frac{1}{500} $ seconds

Therefore, the time period of the vibration is $ 0.002 $ seconds.

Solution:

Identify the part which vibrates to produce sound in the following instruments:

(a) Dholak: The membrane (drumhead) vibrates to produce sound.

(b) Sitar: The strings vibrate to produce sound.

(c) Flute: The air column inside the flute vibrates to produce sound.

Solution:

Difference Between Noise and Music

Noise is unwanted or unpleasant sound that disrupts normal activities and causes discomfort. It is irregular, random, and lacks a definite pitch or harmony. Examples include honking horns, loud machinery, or a crowded street.

Music, on the other hand, is a sound that is organized, harmonious, and pleasing to the ear. It follows certain patterns, rhythms, and melodies, which create a sense of order. Examples of music include songs, symphonies, and instrumental performances.

Can Music Become Noise Sometimes?

Yes, music can become noise in certain situations. When music is played too loudly, or when it disrupts the environment or concentration of others, it can be perceived as noise. Additionally, if the music lacks harmony or has an unpleasant distortion, it may also be considered noise.

Solution:

Sources of Noise Pollution in My Surroundings

1. Vehicles: The sound of cars, buses, and motorcycles on busy roads contributes significantly to noise pollution.

2. Industrial Activities: Factories, construction sites, and machinery can produce loud, continuous noise.

3. Public Events: Loudspeakers used during festivals, weddings, and public gatherings can create noise pollution.

4. Household Appliances: Appliances like mixers, vacuum cleaners, and air conditioners can generate high levels of noise.

5. Aircraft: The noise from airplanes flying overhead can be disturbing, especially near airports.

6. Animals: Barking dogs, street animals, and other loud animals contribute to the surrounding noise.

7. Loud Music: Playing loud music in public spaces, vehicles, or homes adds to noise pollution.

8. Railway Stations: The sounds from trains, their whistles, and station announcements also contribute to noise pollution.

9. Traffic Signals: The honking of vehicles at traffic signals can create a continuous noise disturbance.

Solution:

Noise Pollution and Its Harmful Effects on Humans

Noise pollution refers to the presence of harmful or disturbing sounds in the environment, which can negatively affect human health. It is mainly caused by transportation, industrial activities, construction, and loud music. Here are some ways in which noise pollution is harmful to humans:

• Hearing Loss: Prolonged exposure to loud noise, such as in factories or from vehicles, can cause permanent damage to the ears, leading to hearing loss.
• Stress: Continuous noise can increase stress levels by triggering the body's "fight or flight" response, leading to elevated heart rates and blood pressure.
• Sleep Disturbance: Noise pollution, especially at night, can interfere with sleep, leading to sleep disorders and fatigue, which negatively impact overall health.
• Cardiovascular Problems: Long-term exposure to high noise levels has been linked to an increased risk of heart disease, high blood pressure, and other cardiovascular issues.
• Reduced Productivity: Noise can reduce concentration and focus, leading to lower work performance and academic achievement.
• Impact on Mental Health: Continuous exposure to noise can contribute to anxiety, irritability, and other mental health problems.

Solution:

Which house should your parents buy?

If your parents are considering buying a house, they have two options: one on the roadside and the other three lanes away from the roadside. Let's consider the advantages and disadvantages of each option.

The house on the roadside might be more convenient in terms of easy access to transportation, markets, and other amenities. However, there are also certain drawbacks:

• It could be noisier due to traffic.
• Air pollution might be higher due to the constant movement of vehicles.
• There may be safety concerns with traffic near the house.

On the other hand, the house three lanes away from the roadside might be quieter and more peaceful. It is likely to have cleaner air due to fewer vehicles passing by. However, it may also have some disadvantages:

• It might be less convenient to access shops, markets, and public transport.
• It could be further away from some essential services like hospitals or schools.

So, the decision depends on which factors your parents value more: convenience or a peaceful environment. If they prefer peace and less noise, the house three lanes away from the roadside might be a better choice.

Solution:

Sketch Larynx and Explain its Function

The larynx, also known as the voice box, is a hollow structure located in the throat. It plays an important role in breathing, producing sound, and protecting the trachea against food aspiration. The larynx is made up of cartilage, muscles, and ligaments. It contains the vocal cords that vibrate to produce sound when air passes through them from the lungs. The larynx also helps in regulating the passage of air during breathing.

Function of the Larynx:

• Voice Production: The vocal cords in the larynx vibrate when air passes through them, producing sound. This is essential for speech and communication.
• Airway Protection: The larynx acts as a protective barrier, preventing food and liquids from entering the trachea while swallowing. The epiglottis, a flap of tissue, covers the trachea to prevent choking.
• Regulation of Airflow: The larynx controls the amount of air entering the lungs, helping in the process of respiration.

Diagram of the Larynx

Unfortunately, this is a text-based explanation, so the diagram cannot be displayed here. However, the larynx is located in the neck region, just above the trachea. It is made up of several cartilages, including the thyroid cartilage (Adam's apple), cricoid cartilage, and arytenoid cartilages. The vocal cords are situated within the larynx, and the epiglottis is located just above the opening of the larynx.

Solution:

Lightning and Thunder

Lightning and thunder both occur in the sky at the same time and at the same distance from us. However, lightning is seen earlier and thunder is heard later. This happens because light travels faster than sound. The speed of light is approximately $3 \times 10^8$ meters per second, while the speed of sound in air is about $343$ meters per second at room temperature.

When a lightning strike occurs, the light travels almost instantaneously to our eyes. But the sound waves produced by the thunder take much longer to reach us due to their slower speed. This difference in the speeds of light and sound causes us to see the lightning first and hear the thunder later.