Book Online Demo

Check Your IQ

Try Test

Courses

Offline Centres

The concave lens’ focal length is $15 cm$ , and the image distance is $10 cm$ , then the object distance is ____ $cm$ .

see full answer

Start JEE / NEET / Foundation preparation at rupees 99/day !!

21% of IItians & 23% of AIIMS delhi doctors are from Sri Chaitanya institute !!

An Intiative by Sri Chaitanya

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

The concave lens’ focal length is

15 cm,

and the image distance is

10 cm,

then the object distance is

30 cm

.
A concave lens of focal length

f = - 15 cm

and image distance

v = - 10 cm

(as the image formed is always to the left of the concave lens) is given.
By lens formula,

\frac{1}{f} = \frac{1}{v} - \frac{1}{u}

Where

f

u

and

v

are the focal length, object distance and image distance, respectively.

\Rightarrow \frac{1}{- 15} = \frac{1}{- 10} - \frac{1}{u}

\Rightarrow \frac{1}{u} = \frac{1}{15} - \frac{1}{10}

\Rightarrow \frac{1}{u} = \frac{2 - 3}{30} = \frac{- 1}{30}

\Rightarrow u = - 30 cm

Hence, the object distance is

30 cm

Watch 3-min video & get full concept clarity

JEE

NEET

Foundation JEE

Foundation NEET

CBSE