Page 13 from a science textbook explaining the principles and history of incandescent and halogen light bulbs.

You’ve uploaded a reading passage titled “Incandescent Light Bulbs” from a textbook or worksheet, followed by two comprehension questions. Since I can’t view images directly, I’m working from the text you provided — which appears to be a complete excerpt from the page.

Here’s the solution and explanation for both exercises:

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Exercise 1: Which type of light bulbs, ordinary incandescent or halogen, would last longer? Explain your answer.

✔ Answer: Halogen bulbs would last longer.

Explanation:

The passage explains that in ordinary incandescent bulbs, tungsten atoms evaporate from the hot filament and deposit on the inside of the glass bulb, causing it to darken over time. This darkening reduces light output and eventually causes the filament to thin out and break — ending the bulb’s life.

In contrast, halogen bulbs contain a small amount of halogen gas (like iodine or bromine). When tungsten atoms evaporate from the filament, they combine with the halogen gas to form a compound. This compound circulates back to the hot filament, where it breaks down and redeposits the tungsten onto the filament. This “regenerative cycle” prevents the bulb from blackening and helps maintain the filament’s thickness, allowing the bulb to last longer.

> 📌 *Key sentence from the text:*
> “The halogen atoms combine with the tungsten atoms and carry them back to the filament, where they are redeposited.”

This recycling process is why halogen bulbs have a longer lifespan than ordinary incandescent bulbs.

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Exercise 2: What causes the tungsten atoms to evaporate from the filament?

✔ Answer: The high temperature of the filament causes the tungsten atoms to evaporate.

Explanation:

The passage states that when electricity flows through the filament of an incandescent bulb, it heats up to very high temperatures — so hot that it glows and emits light. At these extreme temperatures, tungsten atoms gain enough energy to escape (evaporate) from the solid filament into the surrounding gas inside the bulb.

This evaporation is a natural physical process — materials tend to lose atoms when heated to very high temperatures (sublimation or evaporation). In incandescent bulbs, this is an unavoidable side effect of producing light by heating a metal filament.

> 📌 *Key sentence from the text:*
> “When electricity flows through the filament of an incandescent bulb, the tungsten wire gets hot enough to glow and give off light. Atoms of tungsten evaporate from the white-hot filament.”

So, the root cause is the intense heat generated by electrical resistance in the filament.

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✔ Final Summary:

- Halogen bulbs last longer because they recycle evaporated tungsten back onto the filament.
- Tungsten evaporates due to the extreme heat of the filament when electricity passes through it.

These answers are based entirely on the information provided in the text. Let me know if you’d like a diagram or analogy to help visualize how halogen bulbs work!