52. | Once the active medium is excited, the first photons of light are produced by which physical process? | |||||||
Answer: Option B Explanation: Spontaneous emission is what you see with most “glow in the dark” toys. You excite the toy by exposing it to bright light, then the toy glows in the dark by spontaneously emitting photons as the excited atoms relax back down to their normal state. |
53. | ‘DTP’ computer abbreviation usually means ? | |||||||
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54. | The average power (in watts) used by a 20 to 25 inch home color television is…? | |||||||
Answer: Option A Explanation: About the same as as the most popular light bulb size. |
55. | What does AC and DC stand for in the electrical field? | |||||||
Answer: Option A Explanation: Electricity is voltage and current. Voltage is electrical pressure, and current is the flow of charged particles. The difference between alternating current (AC) and direct current (DC) is that the electrons in an AC circuit regularly reverse their direction. In a DC circuit electrons always flow in the same direction. |