Chapter 9: Problem 36

If you were lost in the forest and wanted to start a small fire to keep warm or cook a meal using sunlight and a small lens, what type of lens -converging or diverging -would you use and why?

Short Answer

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Answer: A converging lens (convex) would be more appropriate for starting a fire in a forest using sunlight, as it focuses sunlight into a single, concentrated point. This concentrated heat can effectively ignite dry materials, unlike the diffused light produced by a diverging lens.

Step by step solution

Understanding Converging Lenses

Converging lenses, which are also known as convex lenses, have thicker centers than edges. When parallel rays of light pass through a converging lens, they bend inwards and converge at a common focal point. This property allows the lens to concentrate sunlight at a single spot, which can generate heat and potentially start a fire.

Understanding Diverging Lenses

Diverging lenses, also known as concave lenses, have thinner centers than edges. When parallel rays of light pass through a diverging lens, they bend outwards and diverge away from one another. This results in the light being spread out over a larger area, which would not generate enough heat to start a fire.

Comparing the Lenses

To start a fire using sunlight, one must focus the sunlight intensely onto a small area, such as a pile of dry leaves or twigs. Comparing the properties of converging and diverging lenses, we can see that converging lenses focus sunlight into one focal point, while diverging lenses spread sunlight over a larger area, making it less concentrated.

Choosing the Appropriate Lens

Since converging lenses are capable of focusing sunlight into a single, concentrated point, they are the better choice for starting a fire in a forest using sunlight. The concentrated heat generated from the focused sunlight can ignite dry materials more effectively than the diffused light produced by a diverging lens. So, one should use a converging (convex) lens for this purpose.

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If you were lost in the forest and wanted to start a small fire to keep warm or cook a meal using sunlight and a small lens, what type of lens -converging or diverging -would you use and why?

Short Answer

Step by step solution

Understanding Converging Lenses

Understanding Diverging Lenses

Comparing the Lenses

Choosing the Appropriate Lens

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