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. Dangle of incidence equals angle of reflection.
2. Bfrequency remains constant during refraction.
3. Adiffraction is greatest when gap size is comparable to wavelength.
4. Cstanding waves form from opposite-travelling identical waves.
5. Aantinodes are points of maximum displacement.
6. Dresonance means matching the driving and natural frequencies.
7. Bprogressive waves transfer energy; standing waves do not transfer net energy along the medium.
8. Cusing $L = n\lambda/2$, $1.2 = 3\lambda/2$ 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.