Fluorescent bulbs have recently become much more efficient due to the introduction of
A) high-emission phosphor coatings on the inside of the bulb.
B) new types of gases, that glow brighter, within the tube.
C) lower density--i.e., lower pressure--gases within the tube.
D) electronically controlled high-frequency ballasts.
E) longer bulbs.
D
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What does this photograph show?
A) It is a picture of our own Milky Way Galaxy. B) It is a picture of the Andromeda galaxy, located about 2.5 million light-years away. C) It is a picture of a cloud of gas known as the Orion Nebula. D) It is a picture of our own solar system. E) It is a picture of a young star in the process of being born.
Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by ________
A) the human release of chemicals called CFCs into the stratosphere B) the increase in forest fires during recent years C) the fact that our politicians spout a lot of hot air D) human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere
According to the principle of equivalence, gravity is equivalent to
A) acceleration. B) the state of free-fall. C) net force. D) energy. E) velocity.
An electromagnetic wave with components Ey = Eo sin(kx - ?t) and Bz = Bo sin(kx - ?t) is a wave with a frequency of
A) k. B) ?/2?. C) k/?. D) ?. E) ?/?.