Question

^^ How far should an object be placed from a .convex lens of focal length 20 cm to obtain its image at a distance of 30 cm from the lens? What will be the height of the image if the object is 6 cm tall?

Answer 1

Explanation:

Object should be place at a distance of 60 cm on the left side of the convex lens.

Using, m = hl/ho = +v/u we get,

Height of the image,hl = + v/u ho

= + 30/(-60) x 6 = -3 cm

Negative sign shows that the image is inverted and real.

Answer 2

Given :-

• Focal length = 20cm
• V = 30cm
• Height of the object = 6cm

Formula used :-

• 1/f = 1/v - 1/u
• m = Hi/Ho

To Find :-

• Height of the image

Solution :-

$= > \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \\ = > \frac{1}{u} = \frac{1}{v} - \frac{1}{f} \\ = > \frac{1}{u} = \frac{1}{30} - \frac{1}{20} \\ = > \frac{1}{u} = \frac{2 - 3}{60} \: \: \: \: \\ = > \frac{1}{u} = \frac{ - 1}{60} \: \: \: \: \: \: \\ = > u = - 60cm$

Now for Height of the image :-

$= > m = \frac{hi}{ho} = \frac{v}{u} \: \\ = > hi = \frac{v}{u} \times ho \\ = > hi = \frac{30}{ - 60} \times 6 \\ = > hi = - 3 \: \: cm \:$

I hope the answer helps you mate :)

Be brainly ✨