Cutting of Thin Lenses

Q. An equal convex lens of focal length f was cut into two equal parts along a line perpendicular to the principle axis. The focal length of each half is

1. $\frac{f}{2}$
2. f
3. 2f
4. $\frac{3f}{2}$

Q.

A convex lens forms a real image of a point object placed on its principal axis. If the upper half of the lens is painted black,

1. the image will be shifted downward

2. the image will be shifted upward

3. the image will not be shifted

4. the intensity of the image will decrease

Q. A split lens has its two parts separated by distance $a$ and its focal length is $f$. An object is placed at a distance $\frac{3f}{2}$ on the axis of the undivided lens as shown. The distance between the images formed is

1. $a$
2. $2a$
3. $3a$
4. $4a$

Q. A point object O is placed at a distance of $0.3\text{m}$ from a convex lens (focal length $0.2\text{m}$) cut into two halves each of which is displaced by $0.0005\text{m}$ as shown in the figure.



Find the spacing between the images so formed.

1. $0.1cm$
2. $0.5cm$
3. $0.3cm$
4. $1cm$

Q.

If a converging lens of focal length f is cut into two parts and kept as shown in figure, the effective focal length of the combination will be ___