Light passes through a 0.15 mm-wide slit and forms a diffraction pattern on a screen 1.25 m behind the slit. The width of the central maximum is 0.75 cm. What is the wavelength of the light? a. 400nm
b. 450nm
c. 510nm
d. 600nm

b. 450 nm

Explanation:

The wavelength of light can be calculated by using the formula derived in Young's double slit experiment. The formula is as follows:

Δx = λL/d

Δx/2 = λL/2d

where,

Δx/2 = half distance between consecutive dark fringes = width of central maximum = 0.75 cm = 0.0075 m

λ =  wavelength of light = ?

L = Distance of Screen = 1.25 m

d = width of slit = 0.15 mm = 0.00015 m

Therefore,

0.0075 m = λ(1.25 m)/(0.00015 m)

λ = (0.0075 m)(0.00015 m)/2(1.25 m)

λ = 4.5 x 10⁻⁷ m = 450 nm

Thus, the correct option is:

b. 450 nm