Physics Light

1. In a nutshell, what is light?

   Solution

   The smallest quantity of energy that can be transported.

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2. What is a photon?

   Solution

   An elementary particle without a real size that can’t be spit, only created or destroyed.

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3. Can light be understood as both a wave and particle?

   Solution

   Yes, but this is not a completely accurate description of light.

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4. When people talk about light, what do they usually mean?

   Solution

   People usually mean “visible light”, which is a very small band of the electromagnetic spectrum.

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5. What is in the electromagnetic spectrum?

   Solution

   Energy in the form of electromagnetic radiation.

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6. On the electromagnetic spectrum, which waves have the smallest wavelengths?

   Solution

   Gamma rays

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7. What do all waves on the electromagnetic spectrum have in common?

   Solution

   • They all have the wave-particle duality.
   • They all travel at ‘c’, the speed of light.

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8. What makes visible light so special?

   Solution

   Absolutely nothing, except that visible light is the only set of electromagnetic radiation that propagates well in water, which is probably where our eyes first evolved.

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9. How is light created?

   Solution

   A vast range of electromagnetic waves are created when atoms drop from a higher state of energy to a lower one. They lose energy and emit it in the form of radiation.

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10. What two oscillating fields make up electromagnetic radiation?

    Solution

    A magnetic field and an electric field perpendicular to it.

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11. How long does it take light leaving a candle to reach the speed of light?

    Solution

    No time. Light instantly leaves the candle at the speed of light.

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12. Why is 'c' the speed of light?

    Solution

    No one knows. This seems to be a fundamental property of our universe, but we don’t kno why,

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13. What is the speed of light in a vacuum?

    Solution

    299,792,458 m/s (~300,000 km/s, or ~186,000 mi/s)

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14. How does the shoe cover technology at CalTech work?

    Solution

    You step into a gadget on the floor, and a shoe cover automatically wraps around your shoe.

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15. How many FPS (Frames Per Second) can the world's fastest camera take pictures?

    Solution

    ?

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16. About how long does it take light to travel the length of a small water bottle?

    Solution

    2,000 picoseconds

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17. How long is a picosecond?

    Solution

    One picosecond is $1.0^{-12}$ or $0.000000000001$ of a second.

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18. Does the camera show light moving smoothly through space?

    Solution

    No. It seems move erratically or hesitatingly, in small pauses and jumps.

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