This checkpoint covers Lessons 5 to 8: reflection and refraction, diffraction, standing waves, resonance, harmonics, and progressive versus standing wave comparison.
Checkpoint Assessment
1. The law of reflection states that:
2. During refraction into a slower medium, which quantity stays constant?
3. Diffraction is greatest when:
4. A standing wave on a string is formed by:
5. In a standing wave, an antinode is a point of:
6. Resonance occurs when:
7. Which statement correctly compares progressive and standing waves?
8. A string fixed at both ends has length 1.2 m in the third harmonic. The wavelength is:
9. Explain what changes and what stays the same when a wave refracts into a new medium. 3 MARKS
10. Explain why longer wavelengths diffract more noticeably than shorter wavelengths through the same gap. 3 MARKS
11. Compare a progressive wave with a standing wave, and then calculate the wavelength of the second harmonic on a string of length 0.80 m. 4 MARKS
1. D — angle of incidence equals angle of reflection.
2. B — frequency remains constant during refraction.
3. A — diffraction is greatest when gap size is comparable to wavelength.
4. C — standing waves form from opposite-travelling identical waves.
5. A — antinodes are points of maximum displacement.
6. D — resonance means matching the driving and natural frequencies.
7. B — progressive waves transfer energy; standing waves do not transfer net energy along the medium.
8. C — using $L = n\lambda/2$, $1.2 = 3\lambda/2$ so $\lambda = 0.80\ \text{m}$.
Q9 (3 marks): During refraction, the wave changes speed when it enters the new medium, and this usually changes its direction as well. Because $v = f\lambda$, the wavelength changes too. The frequency stays constant because it is set by the source.
Q10 (3 marks): Diffraction depends on how the wavelength compares with the gap size. Longer wavelengths are more comparable to a given gap, so they spread out more after passing through it. Shorter wavelengths passing through the same gap spread less noticeably.
Q11 (4 marks): A progressive wave travels through a medium and transfers energy in the direction of propagation. A standing wave is a stationary pattern with fixed nodes and antinodes and no net energy transfer along the medium. For the second harmonic on a string fixed at both ends, $L = 2\lambda/2$, so $\lambda = L = 0.80\ \text{m}$.
Tick when you have finished the checkpoint and checked the answers.