Question

An object is placed at a distance of 60 cm from a concave lens of focal length 30 cm . find image distance using lens formula. List 4 characteristics of the image formed by the lens in this case. Draw ray diagram to support your answer.

Answer 1

Answer: The image is virtual,erect, small and image is formed at 20 cm from the lens.

Explanation:

Given that,

Distance of the object u = -60 cm

Focal length f = -30 cm

Using lens formula,

$\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

$\dfrac{1}{-30}=\dfrac{1}{v}-\dfrac{1}{-60}$

$\dfrac{1}{v}= \dfrac{1}{-20}$

$v = -20\ cm$

The magnification is

$m = \dfrac{v}{u}$

$m = \dfrac{-20}{-60}$

$m = \dfrac{1}{3}$

Hence, The image is virtual,erect, small and image is formed at 20 cm from the lens.

Answer 2

Answer:

The image is virtual,erect, small and image is formed at 20 cm from the lens.

Distance of the object u = -60 cm

Focal length f = -30 cm

Using lens formula,

The magnification is

Hence, The image is virtual,erect, small and image is formed at 20 cm from the lens.