Final answer:
The intensity variations in Young's double-slit experiment result from constructive and destructive interference, colored fringes with white light arise due to different wavelengths interfering at different angles, and a polaroid halves the light intensity due to polarization.
Step-by-step explanation:
In the context of Young's double-slit experiment, the observations mentioned can be explained as follows:
- The resultant intensity at any point on the screen varies between zero and four times the intensity due to one slit because of constructive and destructive interference. When the path difference between light from the two slits is a multiple of the wavelength (constructive interference), the waves combine to create a bright fringe with maximum intensity, which can be up to four times the intensity of a single slit. Conversely, when the path difference is a half multiple of the wavelength (destructive interference), the waves cancel out, leading to zero intensity and a dark fringe.
- When white light is used, the different wavelengths in white light each have different angles for constructive interference, leading to a spread of colors seen as colored fringes. The central region typically appears white because all colors constructively interfere at the center, but at angles off the center, different colors appear due to variations in their path differences leading to separate and colored interference fringes bordering the central white fringe.
- The intensity of light transmitted by a polaroid is half the intensity of the light incident on it because a polaroid filter polarizes light. The incident light contains waves vibrating in all planes, but the polaroid only allows light waves vibrating in one plane to pass through, effectively blocking half the intensity of unpolarized incident light.