Unit 6: Waves, Sound, and Physical Optics
Physics 2 · Unit 6 · Paper 3

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 1Paper 2Paper 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 3” 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 35 min 32 points0/17 attempted
1

Transverse vs longitudinal waves

2

Why a grating is sharper

3

What changes when a wave enters a new medium

4

Why a closed pipe sounds an octave lower

5

Anti-reflective coatings

6

Single slit is reversed

7

Diffraction and wavelength

8

Thin film thickness for constructive reflection

9

What changes every harmonic

10

Doppler effect direction

11

Why sound needs a medium and light does not

12

Standing waves on a string

Short answer 1. Define or explain: Diffraction grating vs double slit

3 pts

Short answer 2. Define or explain: Harmonics on a string

3 pts

Short answer 3. Define or explain: Boundary conditions choose the frequencies

3 pts

Short answer 4. Define or explain: Polarization

3 pts

Free response

8 pts

Monochromatic light of wavelength 600 nm in vacuum passes through two narrow slits separated by 0.12 mm and falls on a screen 2.0 m away. (a) Calculate the distance on the screen between the central bright fringe and the second-order bright fringe. Show your work. (b) The entire apparatus is submerged in water of index 1.33. Calculate the new fringe spacing and explain, in terms of what physically changes, why it differs from your answer in part (a). (c) The apparatus is returned to air, and one slit is covered. Describe how the pattern on the screen changes, and state the condition satisfied at the DARK fringes of the new pattern. (d) A thin film of index 1.40 is deposited on a glass plate of index 1.52 and illuminated from air with the same 600 nm light. Determine whether the reflection from each surface undergoes a half-wavelength phase shift, and calculate the minimum nonzero film thickness that produces constructive interference in reflection.

Calculate the distance to the second-order bright fringe.

Calculate the fringe spacing in water and explain what physically changed.

Describe the single-slit pattern and state the dark-fringe condition.

Count the phase shifts and calculate the minimum film thickness for constructive reflection.