Question

A girl placed an object (Candle) at a distance of 15m from a concave mirror whose focal length 10m. find the image distance?​

Answer 1

Answer:

Given that

u= -10 cm

f= 15 cm

Find out

We need to find v

Formula

We know the formula

1/f = 1/v + 1/u

Therefore, 1/v= 1/f – 1/u

Substituting the known values in the above equation we get,

1/v= 1/15 + 1/10

1/v = (2+3)/30 (lcm)

Hencev=5/30 = 6 cm

v= 6cm

Nature of the image: The image is formed behind the mirror and it is virtual and erect.

Answer 2

Given :

In concave mirror,

Object distance : 15 cm.

Focal length : 10 cm.

To find :

The image distance of the mirror.

Solution :

Using mirror formula that is,

» A formula which gives the relationship between image distance, object distance and focal length of a sperical mirror is known as the mirror formula .i.e.,

$\boxed{\bf \dfrac{1}{v} + \dfrac{1}{u} = \dfrac{1}{f}}$

where,

• v denotes Image distance
• u denotes object distance
• f denotes focal length

By substituting all the given values in the formula,

$\dashrightarrow\sf \dfrac{1}{v} + \dfrac{1}{u} = \dfrac{1}{f}$

$\dashrightarrow\sf \dfrac{1}{v} + \dfrac{1}{ - 15} = \dfrac{1}{ - 10}$

$\dashrightarrow\sf \dfrac{1}{v} - \dfrac{1}{15} = \dfrac{1}{ - 10}$

$\dashrightarrow\sf \dfrac{1}{v} = \dfrac{1}{ - 10} + \dfrac{1}{15}$

$\dashrightarrow\sf \dfrac{1}{v} = \dfrac{ - 3 + 2}{30}$

$\dashrightarrow\sf \dfrac{1}{v} = \dfrac{ - 1}{30}$

$\dashrightarrow\sf v = - 30 \: cm$

Thus, the position of the image is -30 cm.