Physics Quiz 3

Hypermetropia, also known as long-sightedness, is a defect of vision in which a person can't see the nearby object clearly (appears blurred), though can see the distant objects clearly. The near point of a hypermetropic eye is greater than 25 cm.

Tungsten metal is used for making the filament of electric bulbs because it has a very high melting point. Due to its high melting point, the tungsten filament can be kept white-hot without melting away.

A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. It swings back and forth in a precise time interval. A pendulum clock takes 1 second to move from one extreme to the other extreme, so its time period is 2 seconds.

Lambert's law is related to Illumination. This law stated that the loss of light intensity when it propagates in a medium is directly proportional to intensity and path length.

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.

Sound travels fastest through solids. This is because molecules in a solid medium are much closer together than those in a liquid or gas, allowing sound waves to travel more quickly through it. The speed of sound: in glass is 5640 m/s, in steel is 5960 m/s, in the air is 343 m/s and in water is 1452 m/s.

Rectilinear propagation describes the tendency of electromagnetic waves (sunlight) to travel in a straight line. Eclipses occur due to the rectilinear propagation of light. Whenever an obstacle is placed in the path of light, the shadow of the obstacle is seen on the other side.

The freezing and melting point of water is 0°C. The liquid form of water starts to become solid (ice) and solid (ice) starts to become liquid (water) at this temperature. Hence, at 0°C water exists in both liquid (water) and solid (ice) states.

Pure water is a bad conductor of electricity because it is feebly ionized. The presence of ions is necessary in order for any solution to conduct electricity. Pure water is free from any kind of acids, bases or salts. Hence, it does not conduct electricity due to the absence of ions.

The concept was first proposed by Herman Potocnik in 1928 and popularised by the science fiction author Arthur C Clarke in a paper in Wireless World in 1945.