20091029

Online reading assignment question: blue nebula composition

Astronomy 210, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

(The following question was asked before a presentation on interstellar matter, detailing characteristics of emission, reflection, and dark nebulae.)

A blue nebula is composed of __________. (Graded for completion.)
(A) Hydrogen gas.
(B) Very small dust particles.
(C) Dense clumps of large dust particles.
(D) Helium gas.
(E) (I'm lost, and don't know how to answer this.)

Student responses (pre-instruction)
Sections 70160
(A) : 13 students
(B) : 9 students
(C) : 7 students
(D) : 3 students
(E) : 0 students

Correct answer: (B)

Very small dust particles will scatter short-wavelength (blue) light in all directions more than scattering longer wavelengths, such that this nebula will appear blue in color.

(The same question above was asked of students in a different section, following the presentation on interstellar matter, detailing characteristics of emission, reflection, and dark nebulae.)

Student responses (post-instruction)
Sections 70158
(A) : 9 students
(B) : 14 students
(C) : 8 students
(D) : 4 students
(E) : 3 students

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