Explanation:
Seismic refraction is the bending of the seismic waves as they pass geological layers of the earth due to different densities. This is especially true for Primary waves because they can pass through all the layers of the earth both liquid and solid.
Seismic reflectivity is the bouncing back of seismic waves at a boundary of geological layers due to different densities or subsurface formation. This is especially true for secondary waves that are unable to pass through liquid layers of the earth like the outer core and mantle. When they reach the boundary of these layers they bounce back towards the earth's surface.
These properties of P and S waves are used to ‘auscultate’ the epicenter of an earthquake by triangulation.
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Answer:
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Answer:
Explanation:
Given
inclination 
initial speed 
Point of release is 45 m above the ground
Considering stone to be a projectile, so time taken by projectile for its zero vertical displacement is



Now after completing zero vertical displacement , stone needs to travel another 45 m in downward direction with initial speed u=20\sin 30

where, 






thus total time time required is 
vertical velocity just before hitting



Horizontal velocity 
Net velocity Just before hitting 


Answer:
<em>C. the blue colour of the Earth's sky</em>
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Explanation:
The Pleiades is a cluster of sister stars that are among the closest star cluster to earth.
The reflection nebula of the Pleiades is due to the scattering of the blue light from the hot blue luminous stars that dominate the star cluster. Th blue light is scattered from dust molecules, thought to be predominantly carbon compound like diamond dusts, and other compounds like iron.
The blue colour of the Earth's sky is the closest terrestrial phenomenon to the reflection nebula. On a clear cloudless day, molecules in the air scatter the blue component of light more than the other component colours of white light, giving the sky its characteristic blue coluor.
The common characteristics of the luminous nebula and the Earth's blue sky is that they both have their light scattered by the presence of small particles.