Why does a swimmer under water see the color of seawater as greenish blue?
What will be an ideal response?
Answer: Water is a strong absorber of infrared radiation because its molecules resonate to the frequencies of infrared light. Water also absorbs visible red light, but not so much. So water is weak in reflecting red light (it can't absorb and reflect the same light!). To say it weakly reflects red light is to say it strongly reflects the complementary color of red, which is cyan (greenish blue).
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Which of the following elements is the physical basis of life on Earth?
A) Nitrogen B) Oxygen C) Carbon D) Hydrogen
A conical pendulum is constructed with a string 2.5 m in length. The pendulum is set in horizontal circular path about the vertical axis. If the angular velocity of the conical pendulum is a constant 2.8 rad/s, then the angle the string makes with the vertical axis is
A. 48 degrees. B. 60 degrees. C. 71 degrees. D. 75 degrees. E. 80 degrees.
A proton (+1.6 × 10^?19 C) moves 20 cm on a path in the direction of a uniform electric field of strength 2.4 N/C. How much work is done on the proton by the electrical field?
a. 7.7E–20 J b. ?7.7E–20 J c. 1.8E–19 J d. ?8.6E–20 J e. zero
In a transformer, the power input
A) is larger than the power output. B) is equal to the power output. C) is smaller than the power output. D) can be either larger or smaller than the power output.