<span>The line that is drawn perpendicular to the point at which a wave intersects a boundary is know as the Normal .
When the normal is drawn, the incident ray makes an angle with it known as the angle of incidence and the reflected ray makes an angle with it known as the angle of incidence. These angles are always equal.
The refracted ray makes an angle with the normal known as angle of refraction. The sin of angle of incidence to the sin of angle of refraction is called the refractive index( </span>μ= <span>sin i / sin r) .
hope all of it helps you!</span>
Answer:
Explanation:
Given
angular velocity 
Combined moment of inertia of stool,student and bricks 
Now student pull off his hands so as to increase its speed to suppose 
rev/s
After Pulling off hands so final moment of inertia is
Conserving angular momentum as no external torque is applied
It would be Joules.
Workdone is measured in Joules.
Workdone = Force * distance
Force = mass * acceleration
= kg * ms⁻²
= kgms⁻²
Distance = m
So, Force * distance
kgms⁻² * m
Apply laws of indices that says
x² * x³ = x²⁺³ = x⁵
Therefore, It would be kgm²s⁻²
m¹ * m¹ = m¹⁺¹ = m²
s⁻² is also = s / 2
