Final Exam Jan 2020

(1) Electromagnetic wave at 2.45 GHz hits the rotational frequency of water molecules, and is used in all microwave ovens.

(2) In microscopic world, higher temperature means faster movement types of atoms and molecules, including rotation.

(3) When matter change from liquid to gas state, it needs to absorb thermal energy from its environment.

(4) CFCs are bad refrigerant because that contain fluorine and will destory ozone layer.

(5) The general working principle of any amplifier is that a strong output signal/power is controlled by a weak input signal/power.

(6) A large loudspeaker cone is heavy, it requires high frequency force to drive, whereas a small cones is lighter, it requires low frequency force to drive.

(7) Non-spectral colors are those can not be found in a rainbow, such as purple.

(8) When red light and green light add up, it looks yellow to all land animals.

(9) Inside a LC circuit, only one frequency of driving EM wave from antenna can achieve resonance , this is why tuner can select a specific station in a radio receiver.

(10) Ionosphere can reflect radio wave because at that very high altitude there exist small concentration of free moving metallic atoms.