Optics quiz

More questions about Optics

These visible examples show the question style. LearnClash turns the full topic into ranked duels and spaced repetition.

1. 1 Easy

   How does a door peephole show such a wide view?

   Answer: A fisheye lens

   Why: Typical door viewers take in a field of view of about 160 to 200 degrees.

2. 2 Medium

   What shape are sunlit spots under trees in a partial solar eclipse?

   Answer: Crescents

   Why: On ordinary days the same spots are little round pictures of the Sun's disk, each made by a gap acting as a pinhole.

3. 3 Hard

   Which change does covering half a lens make to its image?

   Answer: It gets dimmer

   Why: Every part of a lens sends light from every point of the object to its image, so the uncovered half still builds the whole picture.

4. 4 Easy

   Which material carries the data in undersea internet cables?

   Answer: Glass

   Why: The cables send invisible infrared light near 1,550 nanometers, the wavelength where silica fiber loses the least light.

5. 5 Medium

   Why is there sometimes a big ring around the Moon?

   Answer: Ice crystals

   Why: Six-sided ice crystals bend moonlight by about 22 degrees, which sets the ring's radius at about 22 degrees.

6. 6 Hard

   About how much light does a plain glass surface reflect head-on?

   Answer: About 4%

   Why: At night that small reflection outshines the dim light from outside, which is why a lit room's window looks like a mirror.