Question

A convex lens forms a real and inverted at a distance of 50 cm from it . Where isvthe needle placed in front of the convex lens if the image is equal to the size of the object ? Also find the power of the lens . 3 mark

Answer 1

Experience the Comfort Of Varilux Lenses! High Resolution Vision At Any Distance. Clear Vision Lens. Lens For All Distances. Best Progressive Lens. Easy Adaptive Lens.

Answer 2

v =50 cm

since a same sized, real and inverted image is formed, therefore the object must be placed at the centre of curvature i.e., at 2F1

and since the image is formed at 2F2. hence the diastance b/w 2F1 and O is 50cm.

Thus the needle is placed 50 cm in front of the lens.

R = 50cm

f= 50/2 = 25cm

f= 0.25 m

P = 1/f

P = 1/0.25

P = 100/25

P = 4D

hence the power of the lens is 4D.