Question

13. An object is placed before a concave lens of focal
length 12 cm. The size of the image formed by the
lens is half the size of the object. Calculate the
distance of the object from the lens.​

Answer 1

Answer:

u= -12

Explanation:

F=-12cm

M=+0.5(+be as image formed by concave lens is always virtual)

M=v/u

0.5=v/u

v=0.5u *equation 1

1/F=1/v -1/u *equation 2

1/F=1/0.5u-1/u

1/-12=1/u

therefore u=-12

Answer 2

Answer:

u= -12

Explanation:

F=-12cm

M=+0.5(+be as image formed by concave lens is always virtual)

M=v/u

0.5=v/u

v=0.5u *equation 1

1/F=1/v -1/u *equation 2

1/F=1/0.5u-1/u

1/-12=1/u

therefore u=-12