Final answer:
To observe maxima with a laser and a CD acting as a diffraction grating, aim the laser onto the CD's reflective surface. A diffraction grating produces sharper maxima compared to double slits and noticeable side maxima. The groove spacing on the CD can be determined by analyzing the positions of the observed interference fringes.
Step-by-step explanation:
When using a disc such as a compact disc (CD) as a diffraction grating, to observe interference patterns including maxima above and below the central maximum, you should shine the laser directly onto the reflective surface of the disc. A diffraction grating creates an interference pattern that consists of a central maximum and n-order maxima and minima. The maxima in a diffraction grating pattern are narrower (sharper) than those produced by double slits, and the central maximum is more pronounced than the side maxima in a single slit pattern.
The brightest spot, which is the central maximum, corresponds to the reflected beam at an angle equal to the angle of incidence. The first-order maxima (and higher orders) can be observed on either side of this central maximum. To calculate the spacing of grooves on the CD, one can use the position of the fringes observed on a wall placed at a known distance from the CD. The formula used to calculate the groove spacing involves the angle to the first fringe, the wavelength of the laser light, and the distance from the CD to the wall, utilizing the principle that the path difference between adjacent grooves must be an integral multiple of the wavelength for constructive interference (bright fringes).