Light propagation, optical phenomena, and optical systems. General electric and magnetic phenomena belong in Electromagnetism.
Test your knowledge with these top questions!
What shape does a lone soap bubble usually form as it floats in still air?
A sphere encloses a given volume with the least surface area, so surface tension pulls a free bubble toward that shape.
What does a dark patch near the top of an aging soap bubble often mean?
Dark patches can appear before a bubble bursts, as draining and evaporation leave too little liquid to sustain the film.
Which light can produce the full rainbow of colors seen on a soap bubble?
Under a lamp that emits only one color, a bubble shows bright and dark bands rather than a full rainbow.
What wave effect creates the rainbow colors reflected by a soap bubble?
Light reflects from both sides of the thin film, and the two reflections can reinforce or cancel each other.
In a hot-road mirage, the apparent water is usually an image of what?
Your brain traces the arriving light backward in a straight line, placing the sky's image on the road.
In the concave bowl of a shiny teaspoon held at arm's length, how does a face look?
Reflected light from the top and bottom of your face crosses before forming the image, flipping its orientation.
Why can the same patch of a soap bubble change color when viewed from a different angle?
Angled light travels a different route through the film, changing which colors the reflected waves strengthen.
Why does the Sun often look red near sunset?
The longer route scatters more blue light out of the direct beam, leaving more red and orange light to reach your eyes.
Two polarizing filters block the most light when their filtering directions have which alignment?
The first filter selects one vibration direction, and a crossed second filter blocks that direction.
A convex lens forms a sharp image of a distant tree on paper. Which way up is the image?
Light from the tree's top lands at the image's bottom because the rays cross after passing through the lens.