Explanation:
7.
Of the items listed, only the first three produce light. The first and third do it by heating a solid wire hot enough to make it emit light due to its temperature. The light from a toaster (and from an incandescent bulb, for that matter) is incidental to the infrared radiation it is producing.
The light from a sodium vapor lamp is created by a plasma of sodium vapor excited by the electricity running through it. The arc through the sodium gas is responsible for the description of the light as an "arc light" or "gas discharge light".
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8.
Since the direction of the light does not change from the incident ray to Ray B, the index of refraction of media X and Y must be the same:
- Both substances have the same index of refraction n.
