The angular speed is defined as:
<h2> ω=

</h2>
where



C.
Explanation: Because mirrors are lighter, and they are easier than lenses to make perfectly smooth.
Number a is a correct one
Answer:
B = 0.75 T
Explanation:
As we know that the force on a moving charge in magnetic field is given by the formula

here we have

here we know that



now from above equation we have


Answer: Hot spot
The volcanic hot spot is an area in the mantle from which heat rises as a thermal plume from deep in the Earth.