A projector lens is needed to form an image on a screen 6 times the size of its corresponding object. The screen is located 8.65 m from the lens. What is the required focal length of the lens?
a. 1.44 m
b. 7.41 m
c. 1.24 m
d. 0.721 m
e. 1.73 m
c
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The data points on this graph represent the measured spectrum of the cosmic microwave background, while the solid curve represents a theoretically calculated thermal radiation spectrum for a temperature of 2.73 K. What is the significance of the near-perfect match between the data and the theoretical spectrum?
A) It shows that the cosmic microwave background has a thermal radiation spectrum, just as the Big Bang theory predicts it should. B) It shows that all objects in the universe emit thermal radiation. C) It tells us the average temperature of gas in the Milky Way Galaxy. D) It demonstrates that the universe must contain more dark matter than ordinary matter.
A 3.0-kg block is on a frictionless horizontal surface. The block is at rest when, at t = 0, a force (magnitude P = 2.0 N) acting at an angle of 22° above the horizontal is applied to the block. At what rate is the force P doing work at t = 2.0 s?
a. 2.3 W b. 2.0 W c. 1.4 W d. 1.7 W e. 1.2 W
How much heat is required to increase the temperature of 1.70 moles of an ideal monatomic gas by 23.0 K at constant pressure?
A) 812 J B) 346 J C) 751 J D) 391 J E) 290 J
The summer solstice (at the start of summer) is the point on the ecliptic where the Sun
a. crosses the celestial equator moving north. b. crosses the celestial equator moving south. c. is farthest north of the celestial equator halting its northward movement. d. is farthest south of the celestial equator halting its southward movement.