Physics - Properties of waves (Light and Sound)

Grade 9IGCSE

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

🔑Concepts

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Waves are oscillations that transfer energy and information without the transfer of matter. They can be categorized as transverse or longitudinal.

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Transverse waves: The oscillations are perpendicular to the direction of energy transfer (e.g., light waves, water waves).

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Longitudinal waves: The oscillations are parallel to the direction of energy transfer, consisting of compressions and rarefactions (e.g., sound waves).

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A

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i

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n_1 < n_2

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c

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f

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c = 3.0 \times 10^8 \text{ m/s}

📐Formulae

v = f \lambda

f = \frac{1}{T}

n = \frac{\sin i}{\sin r}

n = \frac{c}{v}

\sin c = \frac{1}{n}

💡Examples

Problem 1:

0.05\text{ m}

Solution:

v = f \lambda = 10 \times 0.05 = 0.5\text{ m/s}

Explanation:

The wave speed is calculated by multiplying the frequency by the wavelength using the standard wave equation.

Problem 2:

c

Solution:

\sin c = \frac{1}{n} = \frac{1}{1.52} \approx 0.6579

Explanation:

To find the critical angle, we use the relationship between the refractive index and the sine of the critical angle, then take the inverse sine.

Problem 3:

2.0\text{ s}

Solution:

v = \frac{2d}{t} \implies d = \frac{v \times t}{2}

Explanation:

2d