Question

Which of the following is true for radial reflection?

• A. Sound emanating from a focus in any direction will always travel along the focal lengths.
• B. The sum of these focal lengths is variable, but it will always travels the same total distance.
• C. Regardless of direction, the ray takes the same amount of time to leave one focus, reflect off of the ellipse and pass through the other focus (since the velocity of sound is the same). So when sound is emitted radially the reflections arrive at the other focus at the same time.
• D. None of the above

Answer 1

Answer: (A), (C)

The correct options are
A Sound emanating from a focus in any direction will always travel along the focal lengths.
C Regardless of direction, the ray takes the same amount of time to leave one focus, reflect off of the ellipse and pass through the other focus (since the velocity of sound is the same). So when sound is emitted radially the reflections arrive at the other focus at the same time.

The sound emanating from a focus in any direction will always travel along the focal lengths. This comes under radial reflections. As the sum of focal lengths is always constant, it will always travel the same distance. So, regardless of the direction, the ray takes the same amount of time to leave one focus, reflect off of the ellipse and pass through the other focus (since the velocity of sound is the same). So when sound is emitted radially the reflections arrive at the other focus at the same time.