Rainbow Quiz
Questions: 16 · 10 minutes
1. Which conditions are best suited to seeing a moonbow?
A bright Moon behind you with rain, spray, or mist ahead
A bright Moon overhead with no moisture in the air
A bright Moon ahead of you and mist directly behind you
A new Moon ahead of you with clear, dry air behind it
2. From the outer edge to the inner edge, what is the usual color order of a primary rainbow?
Violet toward red
Red toward violet
Green toward red, then blue
Blue toward yellow, then violet
3. Why can an observer in an aircraft sometimes see a nearly complete circular rainbow?
The aircraft's motion bends the two ends of the rainbow together
Cabin windows magnify an ordinary arc into a circle
Rainbows naturally become circular only above the clouds
Droplets can surround the viewing direction without the ground or horizon hiding the lower portion
4. How is the color order of a secondary rainbow oriented relative to the primary rainbow?
It begins with green because red and violet cancel out
It is identical, with red on the outer edge of both bows
It is reversed, with red on the secondary bow's inner edge and violet on its outer edge
It varies randomly because each secondary bow uses different colors
5. Why is a secondary rainbow usually fainter than the primary rainbow?
Its light undergoes an additional internal reflection, so more light is lost
It forms only from smaller droplets, which contain less light
It is always farther away and therefore dimmer
Clouds selectively absorb the secondary bow's colors
6. You are using a garden hose on a sunny day. Which setup is most likely to reveal a small rainbow in the spray?
Look toward the Sun with the spray behind you
Stand directly under the spray while looking upward
Place the spray in your shadow and face sideways from the Sun
Keep the Sun behind you and view the spray ahead
7. A rainbow looks bright through polarized sunglasses, but becomes much dimmer when the lenses are rotated. What best explains this?
Rotating the lenses changes the refractive index of the raindrops
The lenses shift the rainbow's wavelengths outside visible light
Rainbow light is partly polarized, so lens orientation changes how much passes through
The rotated lenses block only light arriving from distant objects
8. Why does a rainbow appear as an arc rather than a straight band?
Wind arranges raindrops into a curved sheet
Earth's curved surface bends the emerging light
Clouds block the center of an otherwise straight spectrum
Suitable droplets lie at nearly a fixed viewing angle around the point opposite the Sun
9. Which sequence best describes the path of sunlight through a droplet that contributes to a primary rainbow?
It refracts on entry, reflects twice inside, then leaves without further refraction
It reflects from the front surface, circles the droplet, then exits unchanged
It refracts and disperses on entry, reflects once inside, then refracts again on exit
It passes straight through the droplet and separates into colors afterward in the air
10. Rain is falling ahead of you late in the afternoon. Where should the Sun be for you to have the best chance of seeing a rainbow?
Directly above you
Ahead of you, behind the rain
Behind you, opposite the rain
At either side, level with the horizon
11. Which combination of processes is mainly responsible for a primary rainbow forming in raindrops?
Polarization in clouds, followed by refraction through dry air
Diffraction around each droplet, followed by absorption
Scattering from air molecules, followed by external reflection
Refraction and dispersion as light enters and exits, plus one internal reflection
12. Two people standing several meters apart look at what seems to be the same rainbow. What is actually happening?
Only the taller observer receives refracted light from the bow
Each observer receives rainbow light from a different set of suitably positioned droplets
One sees the primary bow while the other necessarily sees the secondary bow
Both see light from one fixed row of droplets in the sky
13. Sometimes faint extra colored bands appear just inside a primary rainbow. What mainly produces these supernumerary bows?
Interference between light waves traveling along nearby paths through droplets
Separate rainstorms overlapping along the same line of sight
Repeated reflections between the ground and the cloud base
Color filtering caused by dust layered beneath the main bow
14. When white light passes from air into water, how does violet light generally compare with red light?
Violet light refracts more than red light
Violet light refracts less than red light
Both colors refract by exactly the same amount
Red light is refracted, while violet light is only reflected
15. A person walks toward the apparent end of a rainbow. Why can they not reach a fixed endpoint?
The endpoint retreats because raindrops are pushed away by body heat
A rainbow is observer-dependent geometry, not an object at a fixed location
The endpoint is a reflection located beneath the ground
The endpoint exists only while the observer remains completely still
16. On a clear view of a double rainbow, why can the region between the two bows appear relatively dark?
The two bows combine destructively and eliminate all colors between them
Primary-bow rays are concentrated mainly inside that bow and secondary-bow rays mainly outside it, leaving fewer directed into the gap
The secondary bow casts a physical shadow onto the primary bow
Rain cannot fall in the part of the sky between the bows