. One half of a convex lens of focal length 10 cm is covered with a black paper
Can such a lens produce an image of a complete object placed at a distance of 30 cm from the lens? Draw a ray diagram to justify your answer
A 4 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 15 cm. Find nature, position and size of the image.
Ans. (i) Yes. If a convex lens of focal length 10 cm is covered one half with a black paper, it can produce an image of the complete object between F2 and 2F2. The rays of Object 2 F1 light coming from the object get refracted by the upper half of the lens. The image formed will be real inverted and diminished.
(ii) Object height, h1 = 4 cm
Focal length, f = +20 cm
Image distance, v = ?
Object distance, u= -15 cm
Image height, h2 =?
By lens formula,
Negative sign of h2 shows that the image is erect.
Therefore, a virtual, erect, magnified (16 cm) image will be formed at a distance of 60 cm on the same side as of the object by the convex lens.