Diffraction MCQ Level - 1 - Physics MCQ

Explanation: As the whole apparatus is now immersed in water, the wavelength of the light will change. λ’= λ / μ
Therefore, as the refractive index of water is greater than the air, the wavelength of light will decrease. Width of central maxima = 2λ / a
Therefore, as the wavelength decreases, the width of the central maxima decreases.

Width of central maxima is inversely proportional to slit width or aperture size .

The correct answer is: W decreases as b increases

The two lines will be seen distinctly if they are resolved by grating.
Resolving power

∴ The correct option is close to 1000.
The correct answer is: close to 1000

The correct answer is: a bright central disc surrounded by alternate dark and bright concentric rings

dsin(theta) = m (lambda)

If distance between the maximas increases it means sin(theta) will increase so to normalize that d should decrease. It means that ‘d’ should decrease which in turn means that the number of slits per cm will increase.

The correct answer is: on the first minimum of the diffraction pattern of other

The correct answer is: Increase of angle of diffraction w.r.t. change in wavelength

The correct answer is: increases as the total number of lines on the grating increases

Resolving power = nN, where n is order of diffraction and N is the total number of ruling on grating.
N = WL
∴ R^.P  = nWL

where n = 1
R^.P₁ = 1 x 5000 = 5000
R^.P₂ = 1.5 x 4000 = 6000
R^.P₃ = 2 x 2400 = 4800
R^.P₄ = 3 x 1500 = 4500
The correct answer is: W = 1.5 cm, L = 4000

The correct answer is: mN