Inventions quiz

More questions about Inventions

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

1. 1 Easy

   What explosive did Alfred Nobel invent to make blasting safer?

   Answer: Dynamite

   Why: Nobel combined unstable nitroglycerin with porous clay, turning a dangerous liquid into stable solid sticks.

2. 2 Medium

   Where does a barcode scanner detect reflected light?

   Answer: The white spaces

   Why: The black bars absorb laser light, so the sensor actually reads the pattern bouncing off the white spaces.

3. 3 Hard

   What crystal powered the first working optical laser?

   Answer: Synthetic ruby

   Why: Chromium ions inside the synthetic ruby emitted deep red light at 694.3 nanometers when excited by a helical flashlamp.

4. 4 Easy

   What component did James Watt add to make steam engines efficient?

   Answer: Separate condenser

   Why: Condensing steam in a separate chamber prevented wasting heat on reheating the main piston cylinder.

5. 5 Medium

   Who was the modern treadmill first built for?

   Answer: Prisoners

   Why: British prisons installed early treadmills to discipline idle inmates by making them walk rotating steps for hours.

6. 6 Hard

   Which element made up the first working transistor?

   Answer: Germanium

   Why: Early solid-state physicists relied on germanium because contemporary metallurgy could not yet refine silicon to sufficient purity.