Light of wave 500x10 -9 m falls normally on a plane diffraction grating having 8 x 10 +3 lines per cm. The minimum number of images seen is:

Explanation

Explanation is given below.The formula for the number of images formed by a diffraction grating is:nλ = d(sinθ + sinφ)where n is the order of the spectrum, λ is the wavelength of the light, d is the distance between the slits, θ is the angle between the incident beam and the normal to the grating, and φ is the angle between the diffracted beam and the normal to the grating.In this case, the wavelength of the light is λ = 500 x 10^-9 m, the distance between the slits is d = 1/8000 m = 1.25 x 10^-4 m, and the incident beam falls normally on the grating so θ = 0.To find the value of φ for the first order spectrum, we can set n = 1 in the above formula and solve for sinφ:sinφ = λ/d = (500 x 10^-9)/(1.25 x 10^-4) = 0.004Taking the inverse sine of this value, we get:φ = sin^-1(0.004) = 0.23°For the first order spectrum, there will be a bright spot at an angle of 0.23° on either side of the central maximum, giving a total of three images. Therefore, the minimum number of images seen is 3.So, the answer is 3.As it is a numerical, it can have only one possible answer.