Section: Coach Light — How Light Works
This section covers Chapter 1, Lessons 1.1 through 1.4.
Part A — Vocabulary (20 points, 2 points each)
Select the best answer for each question.
1. Visible light refers to:
A) Light that is also visible to bees B) Electromagnetic radiation with wavelengths roughly 380-700 nanometers, which the human eye can detect C) Any sunlight without UV D) Only blue light
2. Lux is:
A) A unit of color quality B) A unit of light intensity at a surface — bright sunlight is around 100,000 lux; indoor lighting 100-500 lux C) A measurement of warmth D) Time of day
3. Color temperature is:
A) The temperature at which light glows B) A measure of the color quality of a light source, expressed in kelvins; lower K = warmer/orange, higher K = cooler/blue C) The same as actual room temperature D) Used only by photographers
4. Melanopsin is:
A) A pigment in the skin that produces melanin B) A light-sensitive protein in ipRGCs, most sensitive around 480 nm (blue-cyan range) C) A retinal disease D) A hormone of the pineal gland
5. ipRGCs are:
A) Photoreceptor cells that detect color B) Intrinsically photosensitive retinal ganglion cells — a third class of light detectors involved in circadian signaling C) Retinal blood vessels D) Cells in the optic nerve only
6. The suprachiasmatic nucleus (SCN) is:
A) A part of the eye B) A small cluster of neurons in the hypothalamus that serves as the master circadian clock C) Located in the pineal gland D) Part of the brainstem only
7. Melatonin is:
A) A skin pigment B) A hormone produced by the pineal gland, primarily at night, signaling darkness to the body C) A neurotransmitter for memory D) A digestive enzyme
8. Cortisol Awakening Response (CAR) is:
A) A 30-60% rise in cortisol in the first 30-45 minutes after waking B) A medical disorder C) A drop in cortisol on weekends D) The same as stress
9. Zeitgeber (German for "time-giver") refers to:
A) A type of clock B) An environmental cue that synchronizes biological clocks; light is the strongest C) A meditation practice D) A measurement of jet lag
10. Entrainment describes:
A) Training a dog B) The synchronization of an internal biological clock to an external rhythm such as the day-night cycle C) A form of memory training D) A type of exercise
Part B — Concept Comprehension (20 points, 2 points each)
Select the best answer for each question.
11. Visible light occupies the part of the electromagnetic spectrum with wavelengths of approximately:
A) 100-400 nm B) 380-700 nm C) 700-1000 nm D) 1-100 nm
12. Direct sunlight at noon is approximately how much brighter than typical indoor lighting?
A) About the same B) About 10 times brighter C) About 200-1000 times brighter D) About a million times brighter
13. The retina contains three types of light-detecting cells. They are:
A) Rods, cones, and lenses B) Rods, cones, and ipRGCs C) Cones, irises, and pupils D) ipRGCs, melanopsin, and cortisol
14. Melanopsin is most sensitive to light wavelengths in the:
A) Red range, around 700 nm B) Blue-cyan range, around 480 nm C) Ultraviolet range, around 350 nm D) Infrared range, around 1000 nm
15. Without external time cues, the average human circadian rhythm runs at:
A) Exactly 24 hours B) Slightly less than 24 hours C) Slightly longer than 24 hours D) Exactly 12 hours
16. "Social jet lag" refers to:
A) Travel-related fatigue B) The pattern of different sleep schedules on weekdays and weekends, producing circadian disruption C) A medical condition requiring surgery D) A form of solar radiation
17. Melatonin is primarily produced by the:
A) Adrenal glands B) Pancreas C) Pineal gland D) Thyroid
18. The cortisol awakening response is:
A) A sharp rise in cortisol within 30-45 minutes after waking B) A drop in cortisol at bedtime C) A side effect of caffeine D) A response to stress only
19. Coach Light's strong warning about sun-staring is because:
A) Sun exposure is always dangerous B) Direct staring at the sun can cause permanent retinal damage in seconds C) The circadian system does not need light at all D) Sunrise contains no useful light
20. Peripheral clocks refer to:
A) Old-fashioned mechanical watches B) Circadian clocks present in cells throughout the body, coordinated by the SCN C) Brain regions in the periphery D) Clocks running at the edge of the day
Part C — Application (30 points, 6 points each)
Write 2-4 complete sentences for each question. Show your reasoning.
21. Explain how the discovery of ipRGCs changed scientific understanding of the eye. What was previously thought, and what changed?
22. Describe how light reaching the eye in the morning is used by the body to set the master clock. Name the structures involved and trace the signal from retina to hormone response.
23. Walk through what happens to melatonin levels across a typical 24-hour day in a healthy person.
24. Why might bright phone screen exposure at 11 p.m. be a problem for the circadian system? Reference specific structures and pigments in your answer.
25. The chapter describes the SCN as a "conductor" of peripheral clocks throughout the body. Explain what this metaphor means and give one practical implication for daily life.
Continue to the next section.