Chapter 18 Sound: Production of Sound Solutions

Maharashtra State Board Class 7 Science Solutions Chapter 18 Sound: Production of Sound

Class 7 Science Chapter 18 Sound: Production of Sound Textbook Questions and Answers

1. Fill in the blanks:

Question a.
Sound is generated by the rhythmic ……………. of any object.
Answer:
vibrations

Question b.
The frequency of sound is measured in ……………...
Answer:
Hertz (Hz)

Question c.
If …………….. of sound is decreased its loudness also decreases.
Answer:
intensity

Question d.
A medium is necessary for …………… of sound.
Answer:
generation

2. Match the pairs.

Question a.

Answer:

3. Give scientific reasons.

Question a.
In earlier times, people used to listen for the arrival of a distant train by putting their ear to the rails.
Answer:

Question b.
The sounds generated by a tabla and sitar are different.
Answer:

Question c.
If you were both on the moon your friend will not be able to hear you call.
Answer: Yes, your friend will not be able to hear your call because sound needs a medium for transmission since it is a mechanical wave it cannot travel through vaccum.

Question d.
We can hear the movement of a mosquito wings but we cannot hear the movement of our hands.
Answer:

4. Write answers to the following questions.

Question a.
How is sound produced?
Answer:

Question b.
What does the intensity of sound depend upon?
Answer:

Question c.
Explain how the frequency of oscillation is related to the length of a pendulum and the amplitude of its oscillation.
Answer:

1. Given an oscillatory motion to the pendulum, the maximum distance between the original position A of the pendulum and extreme position B or C is called the amplitude of oscillation. AB, AC is the amplitude of oscillation.
2. The number of oscillations completed by an oscillator in one second is called the frequency of oscillation.

Relation between frequency and length of a pendulum: If the length of the pendulum increases the period of oscillations also increases.
We know time period of oscillations =
If time period increases, frequency decreases, therefore, if the length of the pendulum increases frequency will decrease.
Relation between frequency and amplitude: Frequency of oscillation is independent of its amplitude of oscillation.

Question d.
Explain the two ways by which the pitch of the sound generated by a stretched string can be changed?
Answer:
1. A string vibrates with a particular fundamental frequency. It is however possible to produce pitches with different frequencies from the same string.

2. The two properties of the string that affect its frequency are length and diameter.

3. When the length of a string is changed, it will vibrate with a different frequency. Shorter strings have higher frequency and therefore higher pitch.

4. When a musician presses her finger on a string, she shortens its length. The more fingers she adds to the string, the shorter she makes it, higher will be the pitch.
Diameter: Thick strings with large diameter vibrate slower and have lower frequency than the thin ones.

Project:

Question a.
The bat, a mammal, flies during the night manoeuvering with the help of the ultrasonic sounds it produces. Find out more about this.

Class 7 Science Chapter18 Sound: Production of SoundImportant Questions and Answers

Fill in the blanks:

Name the following:

Answer in one or two sentences:

Define:

Say True or False with explanation:

Solve the following problems:

Give scientific reasons:

Answer the following:

Use your brainpower!

Answer the following questions: