Physics Quiz 4

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. The wavelength of the Visible Light ranges between 380 nm to 750 nm (3800 to 7500 angstroms). (The limits of the visible spectrum are not sharply defined but vary among individuals)

A photoelectric cell is a device that are used to convert light energy of the sun into electrical energy. It is an electron tube with a photosensitive cathode that emits electrons when illuminated and an anode for collecting the emitted electrons.

A rectifier is a special type of diode that converts alternating current (AC) into direct current (DC).

Aluminium and its alloys are used for making aircraft and rockets, due to their high strength at relatively low density.

A fountain pen works on the principle of gravity and capillary action. Capillary action is the phenomenon where a liquid will automatically draw itself along a very thin tube.

Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. The hair of a shaving brush clings together when removed from water due to Surface tension.

Gas expands more than liquid for the same tiny change in temperature. Hence, gas thermometers are more sensitive than liquid thermometers.

Clear nights are colder than cloudy nights because of radiation. Clouds warm the Earth by absorbing infrared radiation emitted from the surface and reradiating it back down.

A geostationary satellite is an earth-orbiting satellite, placed at an altitude of approximately 35,800 km directly over the equator, that revolves in the same direction the earth rotates (west to east). At this altitude, one orbit takes 24 hours, the same length of time as the earth requires to rotate once on its axis. So they seem stationary, relative to the Earth's surface.

The surface tension of oil is less than cold water, and hence, oil spreads over cold water. However, the surface tension of oil is greater than that of hot water.