Assertion (A) : In a motion picture, usually 24 frames are projected every second over the whole length of the film. Reason (R) : An image formed on the retina of eye persists for about 0.1 s after the removal of stimulus.

The correct answer is Option 1.

Assertion (A) is true because 24 frames per second (fps) is the standard frame rate for motion pictures. This frequency ensures that the transition between individual still images is seamless to the human eye, creating the illusion of continuous movement.

Reason (R) is also true and provides the underlying scientific principle. This phenomenon is known as the Persistence of Vision. When an image is formed on the retina, it persists for approximately 1/10th to 1/16th of a second (roughly 0.1 s) after the stimulus is removed.

Connection: Since the eye retains an image for 0.1 s, projecting 24 frames per second means each frame lasts only about 0.041 s. Because this interval is much shorter than the persistence time (0.1 s), the brain overlaps the images, resulting in fluid motion. Thus, R perfectly explains why A is necessary for cinematography.