Plane angle

plane angle and solid angle

1. CLASS VIII SCIENCE PART VI PLANE ANGLE AND SOLID ANGLE

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

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

4. Examples : Square Rectangle Triangle Circle

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

6. 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.

7. SOLID ANGLE

8. 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?

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

10. The SI unit of solid angle is ‘ steradian ’ and is denoted as ‘ sr ’ = 5cm Surface area r 2 25cm 2

11. 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 1m 2

12. 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

13. 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?