Question

what is the minimum distance between an object and its real image formed by a convex lens of focal length 20cm​

Answer 1

Answer:

1/v + 1/u = 1/f

1/x + 1/x = 1/20

2/x = 1/20

1 = x/40

1 = x/40

x = 40 cm is the minimum distance

Answer 2

Answer:

The minimum distance between an object is  4f

Explanation:

An optical lens is typically made of  round surfaces. If the ones surfaces are bent outwards, the lens is known as a biconvex lens or in reality convex lens. These forms of lenses can converge a beam of mild coming from outdoor and consciousness it to some extent on the alternative side

Let the among item and actual photograph be d.    

Let the gap of item from the lens is x

So the gap of photograph and lens be d-x

the use of the lens equation

1/f=1/u-1/v

1/f=(1/d-x)-1/-d

x=d±$\sqrt{d^{2}-4fd }$ / 2

so for actual x is

$\sqrt{d^{2}-4fd }$ ≥0

so d≥4f

So minimal distance among item and photograph is 4f.

#SPJ3