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Light and Sound - Production of sound through vibrations

Grade 3IGCSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Sound is a form of energy produced when an object vibrates. A vibration is a quick back-and-forth movement (represented as ⇌\rightleftharpoons).

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Pitch is how high or low a sound is. It is determined by the frequency (ff), which is the number of vibrations per second.

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Volume is how loud or quiet a sound is. It is determined by the amplitude (AA), which is the size or strength of the vibration.

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Sound must travel through a medium, such as a solid (ss), liquid (ll), or gas (gg), to be heard.

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When an object vibrates, it causes the particles in the air to vibrate, creating a sound wave that travels to our ears.

📐Formulae

High Frequency(f)=High Pitch\text{High Frequency} (f) = \text{High Pitch}

Large Amplitude(A)=Loud Volume\text{Large Amplitude} (A) = \text{Loud Volume}

Small Amplitude(A)=Quiet Volume\text{Small Amplitude} (A) = \text{Quiet Volume}

💡Examples

Problem 1:

A student plucks a ruler on the edge of a desk. If the ruler vibrates 2020 times in one second, and then they shorten the ruler so it vibrates 5050 times in one second, what happens to the pitch?

Solution:

The pitch of the sound will increase (become higher).

Explanation:

Increasing the number of vibrations per second increases the frequency (ff). Since Pitch∝f\text{Pitch} \propto f, a higher frequency results in a higher pitch.

Problem 2:

Compare two drum beats: Beat AA has a vibration height (amplitude) of 2 cm2\text{ cm}, and Beat BB has a vibration height of 5 cm5\text{ cm}. Which sound is louder?

Solution:

Beat BB is louder than Beat AA.

Explanation:

The volume of a sound depends on the amplitude (AA). Because Beat BB has a larger amplitude (5 cm>2 cm5\text{ cm} > 2\text{ cm}), it produces a louder sound.

Problem 3:

If a tuning fork is struck and placed in a bowl of water (H2OH_2O), ripples are seen on the surface. Why does this happen?

Solution:

The vibrations from the tuning fork are transferred to the water.

Explanation:

Sound is produced by vibrations. When the tuning fork vibrates, it moves the particles of the liquid (H2OH_2O), showing that sound travels through different states of matter.