Astronomy clicker question: masses, densities, and event horizons

Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q10.1

Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the end of their learning cycle (specifically, following the astronomy in-class activity: masses, densities, and escape velocities).

[0.3 points.] Why is a black hole the only object that has an event horizon?
(A) Because of its mass.
(B) Because of its density.
(C) Because of both its mass and density.
(D) (Neither its mass nor density matters.)

Correct answer: (B)

Student responses
Section 5166
(A) : 1 student
(B) : 21 students
(C) : 14 students
(D) : 3 students