Optics puzzles
Total watch time
2h
at 1× speed · exactly 1 hour, 59 minutes, 53 seconds at 1×
| 1× | 1h 59m 53s |
|---|---|
| 1.25× | 1h 35m 54s |
| 1.5× | 1h 19m 55s |
| 1.75× | 1h 8m 30s |
| 2× | 59m 57s |
Plan to finish
About 2 days at an hour a day
Pick a daily pace and the days you'll watch. Ticked videos are skipped.
At one hour a day, every day, this playlist takes about 2 days. Turn on JavaScript to plan around your week.
Videos (5)
2h in total · tick what you've watched
Tick videos you've watched — progress is saved in this browser.
| Watched | ||||
|---|---|---|---|---|
| 1 |
 This tests your understanding of light | The barber pole effect
|
9:57 | 2023-09-01 | |
| 2 |
 How wiggling charges give rise to light
|
21:33 | 2023-09-01 | |
| 3 |
 But why would light "slow down"? | Visualizing Feynman's lecture on the refractive index
|
28:34 | 2023-11-30 | |
| 4 |
 Answering viewer questions about refraction
|
13:25 | 2023-12-03 | |
| 5 |
 How are holograms possible?
|
46:24 | 2024-10-05 |
No videos match that filter.
Embed a badge
Show the watch time in a README or course description — it links back here and updates itself
[](https://playlistduration.com/playlist/PLZHQObOWTQDMKqfyUvG2kTlYt-QQ2x-ui)<a href="https://playlistduration.com/playlist/PLZHQObOWTQDMKqfyUvG2kTlYt-QQ2x-ui"><img src="https://playlistduration.com/badge/playlist/PLZHQObOWTQDMKqfyUvG2kTlYt-QQ2x-ui.svg" alt="Watch time: 2h · 5 videos" width="168" height="20"></a>Add ?speed=1.5 to the image URL for the time at that speed, ?label=Course to change the left text, or ?style=flat-square for square corners.
Want the numbers themselves? GET https://playlistduration.com/api/v1/playlist/PLZHQObOWTQDMKqfyUvG2kTlYt-QQ2x-ui returns them as JSON — free, no key. API docs →
Data from the YouTube Data API as of 2026-09-22 (cached). Private or deleted videos are excluded from totals.