You'll hear that force called different things in different places. It
may be called "electromotive force", "EMF", "potential difference",
or "voltage".
It's just a matter of somehow causing the two ends of the wire
to have different electrical potential. When that happens, the
free electrons in the copper suddenly have a burning desire to
travel ... away from the end that's more negative, toward the end
that's more positive, and THAT's an "electric current".
Answer: 
Explanation:
Given
Wavelength of light 
Screen is 
away
Distance between two adjacent bright fringe is 
When same experiment done in water, wavelength reduce to 
So, the distance between the two adjacent bright fringe is 
Keeping other factor same, distance becomes
Shadows are the absence of light, they are created when an object blocks light. In other words, shadows are the product of light particles, known as photons. These particles “bounce off” of the object without reaching the other side. Therefore light by itself will not form a shadow.
It's 60.... i have used the formula
L=r^2mw
and didn't use the value 0.75...
