Plane angle is the intersection of two straight lines or planes and is two-dimensional. The SI unit of plane angle is the radian. Solid angle is the angle formed by the intersection of three or more planes at a common point and is three-dimensional. The SI unit of solid angle is the steradian, which is the solid angle subtended at the center of a sphere by a portion of the sphere's surface equal in area to the square of the radius. The main differences between plane and solid angle are that plane angle is two-dimensional while solid angle is three-dimensional, and their respective SI units are the radian and steradian.

3. PLANE
What is a plane?
A plane is a flat surface.

4. θ
A plane angle is two dimensional. The two
dimensional shape has only two measurements
i.e., length and breadth.

5. Examples:
Square Rectangle
Triangle
Circle

6. PLANE ANGLE
What is plane angle?
Plane angle is the intersection of two straight
lines or intersection of two planes.
θ
θ

7. The SI unit of plane angle is ‘radian’ and is denoted as ‘rad’.
r
s
r = s
What is radian?
Radian is the angle subtended
at the centre of a circle by an arc
whose length is equal to radius of
the circle.

8. SOLID ANGLE

9. Solid angle is the angle formed by three or more planes
intersecting at a common point.
An angle formed at the vertex of the cone is solid angle.
What is solid angle?

10. Solid angle is three dimensional. A three dimensional shape has three
measurements such as length, breadth and height.
Examples:
CUBE
CUBOID
SPHERE

11. The SI unit of solid angle is ‘steradian’ and is denoted as ‘sr’
= 5cm
Surface area
r2
25cm2

12. What is steradian?
Steradian is the solid angle at the centre of a sphere subtended
by a portion whose surface area is equal to the square of its radius of
the sphere.
1 steradian
Radius 1m
Surface 1m2

13. PLANE ANGLE SOLID ANGLE
Angle between the intersection
of two lines or planes
Angle between the intersection
of three or more planes at a
common point
It is two dimensional It is three dimensional
Unit is radian Unit is steradian
DIFFERENCES BETWEEN PLANE ANGLE AND SOLID ANGLE

14. ASSIGNMENT
•WHAT IS PLANE ANGLE?
•WHAT IS THE SI UNIT OF PLANE ANGLE?
•WHAT IS SOLID ANGLE?
•DEFINE STERADIAN?
•WHAT ARE THE DIFFERENCES BETWEEN
PLANE ANGLE AND SOLID ANGLE?