iGCSE Physics (0625) 3.1 General properties of waves -Exam Style Questions Paper 2 - New Syllabus
▶️ Answer/Explanation
Detailed solution:
Diffraction is the spreading of waves as they pass through a gap or around an edge.
The degree of diffraction depends on the ratio of the wavelength $\lambda$ to the gap width $d$.
Maximum diffraction occurs when the gap width is approximately equal to the wavelength ($d \approx \lambda$).
Conversely, diffraction is least significant when the gap is much wider than the wavelength ($d \gg \lambda$).
In diagram C, the wavefronts are close together (small $\lambda$) and the gap is large (wide $d$).
Therefore, diagram C represents the conditions where the waves will spread out the least after passing through the gap.
▶️ Answer/Explanation
Detailed solution:
Diffraction is the spreading of waves as they pass through a gap. The degree of diffraction (curvature) depends on the ratio of the wavelength $\lambda$ to the gap width $w$.
Maximum diffraction occurs when $\lambda \approx w$, resulting in semi-circular, highly curved waves.
To make waves less curved (less diffraction), we must decrease the wavelength relative to the gap size.
1. Decreasing $\lambda$ makes the waves spread less, appearing flatter/less curved.
2. Changing amplitude has no effect on the shape or curvature of the diffracted wavefronts.
3. Decreasing the gap size $w$ actually increases curvature and spreading.
Therefore, only change 1 results in less curved diffracted waves.
▶️ Answer/Explanation
Detailed solution:
In a longitudinal wave, such as a sound wave, particles of the medium vibrate parallel to the direction of energy transfer.
This motion creates regions of high pressure called compressions and regions of low pressure called rarefactions.
A compression is defined as the part of the wave where the particles are crowded or pushed close together.
In contrast, a rarefaction is where the particles are spread far apart.
Since compressions and rarefactions are unique characteristics of longitudinal waves rather than transverse waves, option A is the only correct definition.