Question

Read the following and answer any 4 questions from 19 (i) to 19 (v)
Ramiya finds out that the short image of the window pane of her Science
laboratory is formed at a distance of 15 cm from the lens she is using, then she
tries to focus the building visible to her outside the window pane without
disturbing the lens. Will she get the image?
1900)
What type of lens is she using?
a) Concave lens
b) Convex lens
c) Flat lens
d) Bifocal lens
19 (ii)
In which direction should she move the screen to obtain a sharp image of the
building?
a) Forwards
b) Backwards
c) Upside
d) Downside
19 (iii) What is the approximate focal length of this lens?
a) 15 cm
b) -15 cm
c) 30 cm
d) -30 cm
19 (iv)
What is the formula for magnification obtained with a lens?
a) Ratio of height of image to height of object
b) Double the focal length.
c) Inverse of the radius of curvature.
d) Inverse of the object distance.​

Answer 1

Answer: should move the screen towards the lens so as to obtain a clear image of the building. The approximate focal length of this lens will be l5 cm. The rays of light coming from distant object such as a tree (or a distant building or electricity pole) can be considered to be parallel to each other. When parallel rays of light are incident on a convex lens, the rays, after refraction, converge at focus on the other side of the lens.Read more on Sarthaks.com - https://www.sarthaks.com/3537/sudha-finds-that-sharp-image-window-pane-her-science-laboratory-formed-distance-from-lens?show=3538#a3538