Question

A thin plastic lens with index of refraction n = 1.71 has radii of curvature given by Ri = -11.5 cm and R2 = 35.0 cm. HINT (a) Determine the focal length in cm of the lens. cm (b) Determine whether the lens is converging or diverging. converging ОО diverging Determine the image distances in cm for object distances of infinity, 7.00 cm, and 70.0 cm. (c) infinity cm (d) 7.00 cm cm (e) 70.0 cm cm

Answer 1

- 11.5 cm R 35.0 em 2 . Index of refraction Ri R & R are the radius of curvature] By Lene maker's formula ; 5° (n-1) ( where f is the focal length of the According to the question, R, is negative and Ra is positive o Hence it is a Canave lens. 눈 22 (0-1) R or, 35 > (121-7) (ts litis) 2 0.71 X -0.0820 em! focal length fo- cm 0.0820 2 - 12.19 com (63) since the focal length i negative, it is diverging a lens

(0) ALAO, by 2 the formula :- 눈 f ů the focal length of the lens v is the image distance from the where u is the object length from the For, Object distance we have, što $ su Hence image distance 2 - 12.19 em The image lies the object. same side on2 that of d) for Object distance u 2-7 em we have i te - + 12.19 tem or t 1 + 12:17 US - 16. 44 cm u 2-70cm For object distance have, u ON 12.18 to 7/30 1219 or t 9mage distance - 14.76 cm