Which statement about dark dust clouds is true?
A) They can be penetrated only with longer wavelengths such as radio and infrared.
B) They block the vast majority of radio waves from our Galaxy.
C) They comprise the majority of the mass of the Galaxy.
D) They can be penetrated only with shorter waves, such as UV and X-ray.
E) Hydrogen and helium are the chief absorbing and scattering agents.
A
You might also like to view...
We can determine the surface temperature of a star from
a. studying its continuous spectrum. b. studying its line absorption spectrum. c. measuring the star's luminosity. d. Both a and c e. All of a, b, and c
Faraday's Law: A flat coil having 160 turns, each with an area of 0.20 m2, is placed with the plane of its area perpendicular to a magnetic field of 0.40 T. The magnetic field changes uniformly from 0.40 T in the +x direction to 0.40 T in the -x direction in 2.0 s. If the resistance of the coil is 16 ?, at what rate is power generated in the coil during this change?
A. 5.0 W B. 10 W C. 15 W D. 20 W
Energy in the Electric Field: A uniform electric field has the strength of 7.0 N/C. What is the electric energy density of this field? (?0 = 8.85 × 10-12 C2/N ? m2)
A. 2.2 × 10-10 J/m3 B. 3.1 × 10-11 J/m3 C. 2.8 × 1012 J/m3 D. 5.5 × 1012 J/m3
The average speed of a horse that gallops 10 kilometers in 30 minutes is
A) 15 km/h. B) 20 km/h. C) 30 km/h. D) 40 km/h.