Basic Physics Online Test
The hair of a shaving brush clings together when removed from water due to:
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.
The frequency of ultrasound waves is typically:
Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz. The frequency of ultrasound waves is above 20 kHz.
Which one of the following lenses should be used to correct the defect of astigmatism?
A cylindrical lens can be used to treat astigmatism. Astigmatism is a condition that results in the abnormal curvature of your cornea or the lens of your eye.
The instrument used to see the distant objects on the Earth is:
The instrument used to see the distant objects on the Earth is a terrestrial telescope. Astronomical telescopes are used for viewing distant stars and planets whereas terrestrial telescopes are used for viewing distant objects on earth.
Sonar is a device that uses sound waves to detect and range objects on or under the surface of the water.
A device which uses sound waves for detection and ranging is called:
In a refrigerator what produces the cooling?
The principle involved in a refrigerator is the rapid absorption of heat by the rapid evaporation of a volatile liquid. Refrigerators use a liquid that evaporates very easily, and this evaporation creates a cooling effect. They then compress the gas into a liquid again, and the whole process starts over.
Conversion of chemical energy into electrical energy occurs in:
A battery is a DC voltage source that converts chemical energy to electrical energy. The chemical reactions in a battery involve the flow of electrons from one material (electrode) to another, through an external circuit.
'Short-sight' in human eye can be corrected by using proper:
A concave lens is used to correct short-sightedness (myopia). A short-sighted person's focus is focusing before the back of the eyeball. The concave lens pushes the rays of light further apart so that they arrive together in proper focus at the back of the eye.
A photoelectric cell converts:
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.
According to the theory of relativity, which of the following always remains constant?
The Special Theory of Relativity is based on Einstein's recognition that the speed of light does not change even when the source of the light moves.
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