Question

Q. i) An object of height 8 cm is placed at a distance of 25 cm in front of a lens having radius of curvature 30 cm The image of an object is obtained on the screen. Determine the nature of lens used. Also find the nature, size and position of image formed.
(ii). A person cannot see the objects beyond 600 cm. Find the power of lens he should use to correct this defect.​

Answer 1

$\boxed{\bf{\blue{\longrightarrow Answer:}}}$

• h = 8cm
• u = -25
• f = 15cm
• Using lens formula
• $\frac{1}{v} = \frac{1}{f} + \frac{1}{u}$
• $\frac{1}{v} = \frac{1}{15} - \frac{1}{25}$
• $v = 37.5$
• $m = \frac{v}{u} = \frac{75}{2 \times - 25} = - 1.5$
• Lens is Convex and image is enlarged real and inverted

For second answer

• u =
• $- \infty$
• v = -600 cm
• Using lens formula
• $\frac{1}{f} = \frac{1}{ - 600} - \frac{1}{ \infty }$
• $p = \frac{100}{600} = 0.166 \: dioptre$