Question

A 2cm tall object is placed perpendicular to the principle axis of the convex lens of focal length 10 cm . The distance of the object from the lens is 15 cm find the nature, size and position of the image form with the ray diagra

Answer 1

Height of the object= +2.0 cm
Focal length f = +10 cm
Object-distance u = -15cm
Image-distance v = ?

1/v - 1/u = 1/f ====>1/v = 1/f + 1/u ===> 1/v = 1/10 + 1/-15
1/v = -2+3/30
1/v = 1/30
v = 30 cm
The positive sign of v shows that the image is formed at a distance of 30 cm on the other side of the optical centre.The image is real and inverted.

Answer 2

Ho = 2 cm. [ Height of object]

F= -10 cm. [ sign convention]

U = -15. [ sign convention]

USING LENS FORMULA,

-1/U + 1/V = 1/F

1/V = 1/F+1/U

PUT VALUES AND SOLVE.U WILL GET THE IMAGE DISTANCE FROM THE LENS.

AFTER THIS,

HI / HO = -V/U .

PUT VALUES AND SOLVE THIS..U WILL GET THE SIZE OF THE IMAGE .