How do you make the shadows of objects appear bigger on the screen​

Totally depends on the nature of the light source. If the light is radiating outward from a point source than the shadow will grow proportionately as the screen is taken further away. If the light is all parallel then the shadow will not increase in size. The size of the shadow of an objects changes due to the change in a position of a source providing light to the object. One can see the size of shadow equals to that of the object when the source is exactly perpendicular to the surface of the object. Size of the shadow decreases on changing the angle and becomes a single point when the source is parallel to the object( at the time of 12 pm, the position of sun is just above of your head. So at this time a minimum size of shadow is formed.)

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."