Basic Physics Online Test
Diamonds are glittering and attractive because light incident on them undergoes:
Diamonds are glittering and attractive because light incident on them undergoes multiple internal reflections. Most of the light rays approaching the surface of a diamond are incident with an angle of incidence more than critical angle. Hence, they suffer multiple reflections and ultimately come out of diamond from the top. This gives the diamond a sparking brilliance.
Cream gets separated out from milk when it is churned. This is due to:
Milk is put in a container in a centrifuge machine and the container is spun at a very high speed. The centrifugal forces act on milk and separate the milk into a cream that is lighter thus floats on top and skimmed milk which is at the bottom. Then cream can be separated from the milk.
Bolometer is used to measure:
A bolometer is an instrument for measuring radiation by means of the rise in temperature of a blackened metal strip in one of the arms of a resistance bridge.
Woollen clothes keep the body warm because:
Woollen clothes keep the body warm because wool is a bad conductor of heat. Woollen clothes are thick and trap air inside forming a layer around the body and so it does not let our body temperature decrease through conduction.
What is 'Teletext'?
Teletext is a standard for displaying text and graphics on the TV screen. Teletext sends data in the broadcast signal, hidden in the invisible vertical blanking interval area at the top and bottom of the screen.
During washing of clothes, we use indigo due to its:
During washing of clothes, we use indigo due to its proper pigmental composition. The combination of yellow and blue colours gives white colour. Hence we add blue indigo to remove yellow tint from the white clothes.
Lambert's law is related to:
Lambert's law is related to illumination. The law states that Illuminance at a point on a plane is proportional to the cosine of the angle of light incident (the angle between the direction of the incident light and the normal to the plane).
The instrument which uses sound waves to measure the depth of oceans is:
The instrument which uses sound waves to measure the depth of oceans is sonar. The word SONAR is an acronym for sound navigation and ranging. It can map the topography of the ocean floor. The device sends sound waves to the bottom of the ocean and measures how long it takes for an echo to return.
What type of mirror is used in a view-finding mirror of a vehicle?
A convex mirror is used as a view-finding (side-view) mirror in a vehicle to see the traffic behind. This is because the image formed in a convex mirror is highly diminished due to which a convex mirror gives a wide field of view of the traffic behind the vehicle.
The oldest type of energy known to man is:
The oldest type of energy known to man is geothermal energy. Geothermal energy is heat (thermal) derived from the earth (geo). Archaeological evidence shows that the first human use of geothermal resources in North America occurred more than 10,000 years ago with the settlement of Paleo-Indians at hot springs.
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