Final Exam Jan 2020

(microwave)

(Y) Electromagnetic wave at 2.45 GHz hits the rotational freqiency of water molecules, and is used in all microway ovens.

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

(fridge)

(Y) When matter change from liguid to gas state, it needs to absorb thermal energy from its environement.

(N) CFCs are bad refridgerants because that contain fluorine and it will destory ozone layer.

(mic)

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

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

(color)

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

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

(radio)

(Y) Inside a LC circuit, only one frequency of driving EM wave from antena can achieve resonace , this is why tunner can select a specific station in a redio receiver.

(N) Ionoshpere can reflect radio wave because at that very high altitute there exist small concentration of free movving metallic atoms.