A Level Physics Practice Exam

Which observation can be made when light goes through a double slit experiment?

1. It creates a diffraction pattern

2. It blocks all the light

3. It causes light to speed up

4. It absorbs light completely

The correct answer is: It creates a diffraction pattern

In the context of the double slit experiment, when light passes through the two slits, it behaves as a wave and creates a diffraction pattern. This phenomenon occurs because the light waves emanating from the two slits interfere with each other. Constructive interference happens where the waves coincide in phase, leading to bright fringes, while destructive interference occurs where they are out of phase, resulting in dark fringes. This alternating pattern of light and dark bands is characteristic of wave behavior and demonstrates the principle of superposition. The other scenarios described are not consistent with the behavior of light in this experiment. Light cannot be blocked completely, as it would still travel without interference. Similarly, the speed of light does not change when passing through slits; it remains constant in a vacuum or uniform medium, and absorption does not occur in a way that would completely eliminate the light passing through the slits. Thus, the observation of a diffraction pattern is a fundamental outcome of the wave nature of light in the double slit setup.