A student has obtained an image of a distant object on a screen to determine the focal length F1 of the given lens. His teacher after checking the image, gave him another lens of focal length F2 and asked to focus the same object on the same screen. The student found that to obtain a sharp image he has to move the lens away from the screen. From this finding we may conclude that both the lenses given to the student were :
A student has obtained an image of a distant object on a screen to determine the focal length F1 of the given lens. His teacher after checking the image, gave him another lens of focal length F2 and asked to focus the same object on the same screen. The student found that to obtain a sharp image he has to move the lens away from the screen. From this finding we may conclude that both the lenses given to the student were :
The correct option is B Convex and F1<F2
As the obtained image is a
real image so it is a convex lens.
Image is formed at the focus of the mirror as the object is far away. As object distance u is same
in both the cases and image distance for mirror having focal length F2 is increasing
as the student is moving the lens away from the screen.
Therefore, focal length of
second lens F2 will be more as compared to focal length of F1.
As the obtained image is a real image so it is a convex lens.
Image is formed at the focus of the mirror as the object is far away. As object distance u is same
in both the cases and image distance for mirror having focal length F2 is increasing
as the student is moving the lens away from the screen.
Therefore, focal length of second lens F2 will be more as compared to focal length of F1.
