Waves, Sound, and Physical Optics unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1 Paper 2 Paper 3

Each paper is built from this unit’s 47 terms and is the same for everyone, so a teacher can assign “Unit 6, Paper 1” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.

Suggested time 37 min 34 points0/17 attempted

String fixed at both ends

Boundary conditions choose the frequencies

Diffraction and wavelength

Thin film: count the shifts

Thin film interference

Resonance

Double-slit interference

Effect of slit separation on fringe spacing

Double slit

Why a grating is sharper

Thin film thickness for constructive reflection

Anti-reflective coatings

Short answer 1. Define or explain: Why a closed pipe skips even harmonics

3 pts

Short answer 2. Define or explain: Single slit is reversed

3 pts

Short answer 3. Define or explain: Beats

3 pts

Short answer 4. Define or explain: Standing waves on a string

3 pts

Free response

10 pts

Students determine the speed of sound in air using a tube closed at one end and open at the other, and a set of tuning forks of known frequency. For each fork, the students adjust the length of the air column until the sound is loudest, indicating resonance at the fundamental frequency. f (Hz) 256 320 384 448 512 L (m) 0.32 0.26 0.21 0.18 0.16

A(i). Explain why the air column resonates only at particular lengths for a given frequency. A(ii). Describe one step that would reduce experimental uncertainty.

B(i). Indicate what quantities the students should graph on the horizontal and vertical axes to obtain a straight line usable to determine the speed of sound. B(ii). Describe how the speed of sound is related to a feature of that graph.

C(i). Calculate the values to be plotted on the horizontal axis. C(ii). Describe the axis labels, with units, and the positions of the plotted points. C(iii). Describe the best-fit line.

D. Using the best-fit line described in part C, calculate an experimental value for the speed of sound in air.