Question

list four characteristics of the image formed by a concave lens of focal length 20cm and the object is placed at a distance of 40 cm from the optical​

Answer 1

It will be :

1 virtual

2 erect

3 diminished

4 same side of the lens

Answer 2

Answer:

The size of the image is two by third of the object and the image distance is $\dfrac{40}{3}$. The image will be placed virtual and erect and diminished.

Explanation:

Given that,

Focal length f = -20 cm

Distance of the object u = -40 cm

Using lens's formula

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

$\dfrac{1}{-20}=\dfrac{1}{v}-\dfrac{1}{-40}$

$\dfrac{1}{v}=\dfrac{-3}{40}$

$v = -\dfrac{40}{3}$

The  image is formed at $\dfrac{40}{3}\ cm$ in same side of the object.

The magnification is

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

$m = \dfrac{40}{3\times20}$

$m = \dfrac{2}{3}$

Hence, The size of the image is two by third of the object and the image distance is $\dfrac{40}{3}$. The image will be placed virtual and erect and diminished.