It takes approximately ______ minutes for sunlight to reach the Earth.
We know that,
Earth-Sun distance = 1.496 x 108m
Velocity of light reaching Earth = 3 x 108 m/s
Time taken by light to reach earth is
=(Earth-sun distance)/(Velocity of light)
= (1.496 x 10^8 m)/(3 x 10^8 m/s)
= 8.31 minutes.
The number of hydrous minerals in the Moh's
scale of hardness is __________.
The hydrous minerals in the Moh’s scale of
hardness are
Talc
Mg3Si4O10(OH)2
Gypsum
CaSO4.2H2O
Apatite
CaS(PO4)3(F1Cl1OH)
Topaz
Al2SiO4(F1OH)2
mechanism of an earthquake. The shaded and unshaded1.9 The depositional feature that forms where a stream emerges from a mountainous region onto a plain is called
(A) alluvial fan
(B) natural levee.
(C) delta
(D) point bar
Alluvial Fans. The alluvial material which flows down from
mountains accumulates at foothills where the stream enters a plain. The deposition occurs due to abrupt change in the gradient of the river valley. Such deposits spread out in the shape of flat fans and are called “alluvial fans”. Usually, the coarse material is dropped near the base of the slope while finer material is carried further out on the plain. Alluvial fans form many adjacent streams along a mountain that may merge to form a long wedge of sediment called “alluvial aprons”.
Deltas. These are submerged equivalents of alluvial fans. “Deltas” are deposits built at the mouths of streams. The deltas are usually triangular in shape with their apex pointed upstream. When a stream enters an ocean or lake, the currents of the flowing water dissipate quickly. This results in the deposition of the series of sedimentary layers which make up the delta. The material of most deltas is well sorted and many deltas are uniformly graded. The structure of a delta deposit is shown
Point Bars. In meandering rivers, sediment deposits occur as point bars. The “point bars” are the crescent-shaped deposits which occur at inside bends of a river channel.
Natural Levees. “Natural levees” are the low ridges which are formed on both sides of a river channel by the accumulation of sediment. They tend to confine the flow of river water into its channel between flood stages. The natural levees occur in rivers which have broad flood plains. During floods, the river overflows its bank and its velocity decreases rapidly. As a result most of the coarse sediment is deposited along the area bordering the river channel and finer sediments are deposited more widely over the flood plain. In this way, successive floods build up ridges on both sides of a river channel, which are called “natural levees.
1.8 The planet which contributes maximum to the angular momentum of the solar system is
(A) Earth
(B) Mars
(C) Jupiter
(D) Saturn
98% of the angular momentum is concentrated in the planets and the remaining 2% is present in the sun. In other words, the sun does not rotate fast enough.
Jupiter is by far the largest of the planets in the solar system. Its mass is 318 times of that of Earth hence contributes maximum to the angular momentum of the solar system as it is proportional to the mass of the body.
1.7 Tsunamis are
(A) gravity waves
(C) Capillary waves
(D) internal waves
(B) acoustic waves
Tsunami: When the ocean floor is abruptely lifted droppped by a submarine earthquake or land slides the entire water column is pushed up and down more than 95% of the potential energy of displaced water is gravitational and less than 5% is elastic energy resulting from compression of ocean floor and water column. The potential energy of the vertical motion is converted to kinetic energy and propogates away from the source as a tsunami
In fluid dynamics, gravity waves are waves generated in a
fluid medium or at the interface between two media when the force of gravity or
buoyancy tries to restore equilibrium. A gravity wave results when
fluid is displaced from a position of equilibrium. The restoration of the fluid
to equilibrium will produce a movement of the fluid back and forth, called a
wave orbit. Gravity waves on an air–sea interface of the ocean are
called surface gravity waves or surface waves, while gravity waves that
are within the body of the water (such as between parts of different densities)
are called internal waves.
Wind-generated waves on the water surface are examples of gravity waves, as are tsunamis and ocean tides.
Wind-generated gravity waves on the free surface of the Earth's ponds, lakes, seas and oceans have a period of between 0.3 and 30 seconds (frequency between 3.3 Hz and 33 mHz).
