a. Define ocal length of a divergent lens. b. A divergetn lens of focal length 30 cm forms the image of an object of size 6 cm on the same side as the object at a distance of 15 cm from its optical centre. Use lens formula to determine the distance of the object the lens and the size of the image formed.

a. Define ocal length of a divergent lens. b. A divergetn lens of foc

1.	a. Define ocal length of a divergent lens. b. A divergetn lens of focal length 30 cm forms the image of an object of size 6 cm on the same side as the object at a distance of 15 cm from its optical centre. Use lens formula to determine the distance of the object the lens and the size of the image formed.
Answer» SOLUTION :a. The distance between the principal focus and the optical CENTRES of the concave lens or diverging lens is called the FOCAL length of a diverging lens. b. `f=-30cm` `h=6cm` `v=15cm, u=?,h=?` Lens formula: `1/v-1/u=1/f` or `(-1)/u=1/f-1/v` `(-1)/15-1/u=(-1)/30` or `(-1)/u=(-1)/30-((-1)/15)` `(-1)/u=(-1)/30+1/15` `(-1)/u=(-15+30)/450` `(-1)/u=1/30` `=u=30` `u=-30cm` The object distance is -30 cm. `m=v/u=(h^(1))/h` `(+15)/(+30)=(h^(1))/6` or `6/2=h^(1)` `h^(1)=3 cm` The height of the image is 3 cm.