I didnt understood what is plane angle and solid angle please explain me.

Plane Angle is defined as the amount of rotation about the point of intersection of two lines that is required to make them overlap on one another. It is measured in radian.

Solid angle is a cone subtended by a surface on the center of the sphere of which the surface is a part. It is defined by the ratio of the area of the surface and square of radius. It is measured in steradian.

In the diagram the area S of the sphere subtends a solid angle, Ω = S/r2

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Pls answer fast 

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In geometry, a solid angle (symbol: Ω) is the two-dimensional angle in three-dimensional space that an object subtends at a point. It is a measure of how large the object appears to an observer looking from that point. In the International System of Units (SI), a solid angle is a dimensionless unit of measurement called a steradian (symbol: sr).

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In geometry, an angle or a plane angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle.[1] Angles are usually presumed to be in a Euclidean plane or in the Euclidean space, but are also defined in non-Euclidean geometries. In particular, in spherical geometry, the spherical angles are defined, using arcs of great circles instead of rays.

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 PLANE ANGLE (d theta) :  It is the ratio of length of arc ds to the radius r.It can be obtained on a plane as it is two-dimensional so  it is a plane angle with its unit radian.

SOLID ANGLE (d omega): It is the ratio of the intercepted area dA of the spherical surface, described about the apex  O as the centre, to the square of its radius. It is three- dimensional ,  it cannot be obtained on a plane, so it is called solid angle with its unit steradian.

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