Question

A He–Ne laser beam is reflected from the surface of a CD onto a wall. The brightest spot is the reflected beam at an angle equal to the angle of incidence. However, fringes are also observed. If the wall is 1.50 m from the CD, and the first fringe is 0.600 m from the central maximum, what is the spacing of grooves on the CD?

a) 0.400 mm
b) 0.600 mm
c) 0.800 mm
d) 1.000 mm

Answer 1

The spacing of grooves on the CD can be determined using the formula for fringe spacing in double-slit interference

Step-by-step explanation:

The spacing of grooves on the CD can be determined using the formula for fringe spacing in double-slit interference, which is given by: d = λL / y where d is the fringe spacing, λ is the wavelength of light, L is the distance from the double-slit to the screen, and y is the distance from the central maximum of the interference pattern to the desired fringe. In this case, we can use the given values:

L = 1.50 m, y = 0.600 m, and the wavelength of the He–Ne laser beam is typically 632.8 nm.

Substituting these values into the formula, we get: d = (632.8 x 10^-9 m)(1.50 m) / 0.600 m Simplifying this expression, we find that d = 1.58 x 10^-3 m or d = 1.58 mm

Therefore, the spacing of the grooves on the CD is approximately 1.58 mm.