Examples from NCERT Book

Class 10
Chapter 10 Class 10 - Light - Reflection and Refraction

## A convex mirror used for rear-view on an automobile has a radius of curvature of 3.00 m. If a bus is located at 5.00 m from this mirror, find the position, nature and size of the image

### Transcript

Example 10.1 A convex mirror used for rear-view on an automobile has a radius of curvature of 3.00 m. If a bus is located at 5.00 m from this mirror, find the position, nature and size of the image Radius of curvature = 3 m We know that Focal length = (πππππ’π  ππ ππ’ππ£ππ‘π’ππ)/2 = 3/2 = 1.5 m Since the focus of convex mirror is behind the mirror, the focal length will be positive Focal length = f = + 1.5 m Now, Bus (Object) is placed infront of the mirror β΄ Object distance will be negative Object distance = u = β5 m Finding position of image Let the image distance = v Using mirror formula, 1/π = 1/π£ + 1/π’ 1/π β 1/π’ = 1/π£ 1/π£ = 1/π β 1/π’ 1/π£ = 1/1.5 β 1/((β5)) 1/π£ = 1/1.5 + 1/5 1/π£ = 10/15 + 1/5 1/π£ = (10 + 3)/15 1/π£ = 13/15 1/π£ = 15/13 π£ = + 1.15 m β΄ Image is produced at a distance of 1.15 m +ve sign indicates that image is formed behind the mirror. Finding size of image Magnification = (βπ£)/π’ = (β (πΌππππ πππ π‘ππππ))/((ππππππ‘ πππ π‘ππππ)) = (β(1.15))/(β5) = 1.15/5 = 115/500 = 23/100 = + 0.23 Since the magnification is less than 1 β΄ Image is diminished and it is smaller in size by a factor of 0.23 And since magnification is positive, β΄ Image is erect Hence, Image is virtual, erect and smaller in size by a factor of 0.23