Which of the following makes it very difficult to detect planets around other stars?
A) Planets are constantly orbiting their stars, so we don't know where to point our telescopes to see them.
B) Planets are typically at least a billion times fainter than their host stars.
C) Planets give off only infrared light, not visible light.
D) Planets orbit too far from their stars to be detected.
B) Planets are typically at least a billion times fainter than their host stars.
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For a certain metal, light of frequency 7.24 × 10-14 Hz is just barely able to dislodge photoelectrons from the metal. (h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J, e = 1.60 × 10-19 C)
(a) What will be the stopping potential if light of frequency 8.75 × 10-14 Hz is shone on the metal? (b) What is the work function (in electron-volts) of this metal?
Express 50°C in °F
A) 50°F B) 45.6°F C) 59.8°F D) 122°F E) 148°F
A balloon will stick to a wooden wall if the balloon is charged
A) negatively. B) positively. C) either of these D) neither of these
A metal sphere of radius 80. mm is charged to a potential of -0.50 kV. With what velocity must an electron be fired toward the sphere if it is to just barely reach the sphere when started from a position 15. cm from the center of the sphere?
What will be an ideal response?