Question

Suppose you wanted to start a fire using sunlight and a mirror. Which of the following statements is most accurate? A) It would be best to use a plane mirror. B) It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature. C) It would be best to use a concave mirror, with the object to be ignited positioned at the center of curvature of the mirror. D) It would be best to use a convex mirror. E) One cannot start a fire using a mirror, since mirrors form only virtual images.

Answer 1

Answer: B) It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature.

Explanation:

To start a fire it is more optimal to use a concave mirror than a plane mirror. This is because the concave mirror allows concentrating sunlight at a point (the focal point) on an object that acts as fuel and ignite the fire there.

For this it is necessary the object to be  positioned between the center of curvature of the mirror and the mirror (its focus). Thus the rays of the Sun, when converging on the focus, will heat the object and make it burn.

Hence, the correct option is B.