Question

The focal point is located 20.0 cm from a double concave lens. an object is placed 12 cm from the lens. Determine the image distance.

Answer 1

Answer: double concave lens. An object is placed 12 cm from the lens. Determine

Explanation: this  is the on I got right on my test

Answer 2

Concept:

Lens formula

1/focal length = 1/image distance - 1/object distance

Given:

Focal length (f) = -20cm

Object position (u) = -12cm

Find:

Image position (v)

Solution:

Applying lens formula

1/focal length = 1/image distance - 1/object distance

1/f = 1/v - 1/u

given as Taking direction of incident ray as positive

Focal length (f) = - 20 cm as focal length of concave mirror is negative

Object Position (u) = -12 cm

1/f = 1/v - 1/u

1/(-20) = 1/v - 1/(-12)

1/(-20) = 1/v + 1/12

1/v = -1/20 - 1/12

1/v = - (1/20 + 1/12)

1/v = - ((12+20)/240)

1/v = - (32/240)

v = -240/32 cm

v = -7.5 cm

So we conclude that after applying the concept of lens formula the image distance found to be 7.5 cm at the side of object only.

#SPJ3