Question

an object is placed perpendicular to the principal axis of a convex lens of focal length 8 centimetre and distance of the object from the lens is 12 cm find the position and nature of the image​

Answer 1

The lens formula is 1/f = 1/v - 1/u

1/v = 1/u + 1/f

1/v = 1/-15 + 1/10

1/v = -2+3/30

1/v = 1/30 or v = 30

The positive sign of v shows that the image is formed at a distance of 30 cm

Answer 2

The positive sign of v shows that the images is formed at a distance of 24 cm on the other side of optical centre and the images is real and inverted.

Explanation:

Given:

• Focal length of convex lens (f) is 8 cm.
• Distance of the object from lens (u) is 12cm.

Formula used:

\frac{1}{f} = \frac{1}{v} - \frac{1}{u}

1/f = 1/v − 1/u

To find:

• position of image.
• nature of image.

Solution:

\frac{1}{f} = \frac{1}{v} - \frac{1}{u}

1/f = 1/v − 1/u

\frac{1}{8} = \frac{1}{v} - \frac{1}{ - 12}

1/8 = 1/v - 1/12

\frac{1}{8} = \frac{ - 12 - v}{ - 12v}

- 12v + 8v = 96−12v+8v=96

4v = 964v=96

v = 96/4

v = 24

• The positive sign of v shows that the images is formed at a distance of 24 cm on the other side of optical centre.
• The images is real and inverted.