Question

Student obtains a blurred image of a distant object on a screen using a convex lens. To obtain a distinct image on the screen he should move the lens _________________

Answer 1

Explanation

1. The convex lens is a lens with an outward curve. It has the ability to converge a parallel beam of light into a point.
2. The images formed by the convex lens are presented in a table given below:

Object location	Ray of Diagram	Image location	Image nature	Image size
Infinity		At ${\mathrm{F}}_2$	Real and Inverted	Diminished
Beyond $2{\mathrm{F}}_1$		Between ${\mathrm{F}}_2$ and $2{\mathrm{F}}_2$	Real and Inverted	Diminished
At $2{\mathrm{F}}_1$		At $2{\mathrm{F}}_2$	Real and Inverted	Same size
Between ${\mathrm{F}}_1$ and $2{\mathrm{F}}_1$		Beyond $2{\mathrm{F}}_2$	Real and inverted	Enlarged
At ${\mathrm{F}}_1$		At infinity	Real and inverted	Enlarged
Between $\mathrm{O}$ and ${\mathrm{F}}_1$		On the same side of the object	Virtual and erect	Enlarged

1. So to obtain a distinct image of an object on the screen, the student should move the lens toward the screen.
2. The second focus of the lens will behave as a screen.
3. It can be observed that, when an object is placed at infinity, the image is obtained at the focus of the lens.

Hence the answer is to move the lens toward the screen.