Question

a concave mirror of focal length 30 cm forms an image having twice the size of object .for the virtual position of object ,the position of object will be at​

Answer 1

Answer:

position of object is at 15 cm from the pole

Answer 2

We know that the focal length of a concave mirror is 30 cm.

We also know that image having a twice the size of the object for the virtual position of the object.

means, the magnification of the image is 2.

→ 2 = –v/u

→ –2u = v

Now, for the position of the object we will use the mirror formula.

$\implies { \underline{ \boxed{ \sf{ \frac{1}{f} = \frac{1}{v} + \frac{1}{u} }}}} \\ \\ \implies \sf{ - \frac{1}{30} = - \frac{1}{2u} + \frac{1}{u} } \\ \\ \implies \sf{ - \frac{1}{30} = \frac{ - 1 + 2}{2u} } \\ \\ \implies \sf{ - \frac{1}{30} = \frac{1}{2u} } \\ \\ \implies \sf{ - 2u = 30} \\ \\ \implies {\boxed{ \mathfrak{\pink{ u = - 15 \: cm}}}}$

We're having,

→ v = –2u → v = -2 × -15 → v = 30 CM