Question

Find the magnification when an object is kept 15 cm in front of a concave mirror of
focal length 10 cm. And also find where the image will be formed. ( 3 marks )
4.) What will happen to the magnification and image if in the previous question concave
mirror is replaced by convex lens of the same focal length?

Answer 1

Dear Student
$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$
u= -10 cm
f= -15 cm
Putting it we get v= 30 cm
Now m=-v/u = 3
Image will be virtual, erect, magnified 3 times and formed 30 cm behind mirror.

4) For convex lens, formula will be
$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$
u= -10 cm
f= 15 cm
Putting it in formula, we get v= -30 cm
m= v/u= 3

Image will be virtual, erect, magnified and 30 cm from lens, towards object side.

Regards