Physics Online Quiz

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.

White and black combination of colours is the most convenient during day and night time. Black text on a white background is best, since the colour properties and light are best suited for the human eye. That's because white reflects every wavelength in the colour spectrum.

Bats can fly in the dark because they generate ultrasonic sound waves. Bats are guided by ultrasonic waves which they produce and enable them to fly in the dark.

In economics, economic equilibrium is a situation in which economic forces such as supply and demand (internal factors) are balanced and in the absence of external influences, the values of economic variables will not change.

When the medium is dense, the molecules in the medium are closely packed, which means that the sound travels faster. Therefore, the speed of sound increases as the density of the medium increases.

Crooks glass is used for sunglasses. Crooks glass mainly comprises of cerium oxide (CiO₂), which absorbs the ultraviolet radiation from the sun.

A nano particle is an ultra fine unit with dimensions measured in nano metres (1 nm = 10⁻⁹ metre).

The swing of a spinning cricket ball in the air can be explained on the basis of turbulence caused by wind.

A simple microscope is a magnifying glass that has a single or double convex lens with a short focal length.

Nuclear Fusion reactions power the Sun and other stars. In a fusion reaction, two light nuclei merge to form a single heavier nucleus. The process releases energy because the total mass of the resulting single nucleus is less than the mass of the two original nuclei.