Questions

The ultraviolet rays have high frequency and shorter wavelength are converted to visible white light with lower frequency and greater wave length

Optical illusion is what that refers to persistence of vision with a principle that multiple images blend into a single image in human mind and what is showed in cinema.

Hence, Persistence of vision is the principle behind cinema.

Microsoft Excel is a spreadsheet developed by Microsoft for Windows, macOS, Android and iOS. It features calculation, graphing tools, pivot tables, and a macro programming language called Visual Basic for Applications.

As against malloc(), calloc() needs two arguments, the number of elements  to be allocated and the size of each element. For example,

 p = (int *) calloc (10, sizeof (int));

would allocate space for a 10- integer array. Additionally, calloc() would also set each of this element with a value 0.

Thus the above call to calloc() is equivalent to:

p = (int *) malloc (10 * sizeof (int));

memset (p, 0, 10 * sizeof( int ));