Which of the following is TRUE?
A) Visible light makes up the greatest part of the electromagnetic spectrum.
B) In a vacuum, electromagnetic waves all travel at the same speed, the speed of light.
C) Ultraviolet light has the shortest wavelength of any electromagnetic wave.
D) A blackbody emits all its radiation at a single wavelength or frequency.
E) Electromagnetic waves cannot travel through empty space.
Ans: B) In a vacuum, electromagnetic waves all travel at the same speed, the speed of light.
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A long solenoid (1000 turns/m) carries a current of 25 mA and has an inside radius of 2.0 cm. A long wire which is parallel to and 4.0 cm from the axis of the solenoid carries a current of 6.0 A. What is the magnitude of the magnetic field at a point on the axis of the solenoid?
a. 51 ?T b. 61 ?T c. 43 ?T d. 81 ?T e. 1.4 ?T
A farsighted person has a near point distance greater than the normal distance of 25 cm. Neglecting the eye-lens distance, which approach will yield an appropriate corrective lens for this condition?
1.The corrective lens should have a focal length equal to the normal near point distance, i.e., 25 cm. 2.The corrective lens should have a negative focal length equal in magnitude to the normal near point distance, i.e., –25 cm. 3.The corrective lens should make an object at a distance equal to the near point appear to the eye to be at a distance of 25 cm. 4.The corrective lens should make an object at a distance of 25 cm appear to the eye to be at a distance of the near point.
What sorts of materials serve as moderators in nuclear reactors?
a. water c. graphite b. boron d. concrete
An incompressible fluid is flowing through a vertical pipe with a constriction. The wide section is 2.00 cm in diameter and is at the top of the pipe. The pressure of the fluid in the wide section at the top is 200 kPa. The velocity of the fluid in the wide section is 4.00 m/s. The narrow section is located 4.00 m below the wide section. What is the diameter of the narrow section for the pressure of the fluid in the narrow section to equal the pressure in the wide section? (density of the fluid is 680 
A. 1.50 cm B. 1.43 cm C. 1.36 cm D. 1.28 cm E. 1.15 cm