Answer: Option (A)
Explanation: Silica rich magma are those in which the magma has more than 65 % of silica content. The higher the silica content, the higher is its viscosity i.e viscosity of a magma is directly proportional to the silica content of magma.
This highly viscous magma inside the volcanoes moves sluggishly and mostly gets concentrated in the vents and seals them. With time, when the pressure exerted by the magma is too high, it creates violent eruptions through the vents.
Thus, the correct answer is option (A).
Answer:
A. Highly viscous and associated with violent eruptions
Explanation:
Most silica rich magma have high viscosity and huge amount of trapped gases within them. As they continue to upwell and expand, the gases causes violent eruptions near Volcanoes. Most granitic/rhyolitic magma are silica rich.
interference
B
reflection
C
refraction
D
diffraction
Answer: Refracrion
Explanation: it is the bending of light
The birds can glide in the air without moving their wings by maintaining the thrust of the air by their weight and move downward at a very slower rate.
Further Explanation:
The birds have a capability of flying high in the air without flapping their wings and still not falling down rather they glide downwards due to the up thrust of the air. This technique of the birds to keep them in the air without flapping their wings is termed as soaring.
The soaring birds make use of the air current and its thrust on their primary wings so that there is no turbulence experienced by them due to the pointed tips of their primary wings.
The birds should possess some mass in order to maintain a balance between the thrust and the weight of their body. That’s why the small birds are not able to maintain their flight but the bigger birds like vulture, eagle etc. experience sufficient air drag in order tio maintain their flight.
Thus, the birds can glide in the air without moving their wings by maintaining the thrust of the air by their weight and move downward at a very slower rate.
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Answer Details:
Grade: High School
Subject: Physics
Chapter: Up thrust
Keywords: Airborne, flapping wings, birds, soaring, vultures, weight, maintain flight, gliding, move downward, turbulence, primary wings.