Q145 / 160 · AP EAMCET 2021 (20 Aug Shift 1) · Physics

The position of the direct image obtained at O , , when a monochromatic beam of light is passed through a plane transmission grating at normal incidence is shown in figure. The diffracted images A,B and C correspond to the first, second and third order diffraction. When the source is replaced by another source of shorter wavelength

Figure

  • A
    all the four will shift in the direction C to O
  • B
    all the four will shift in the direction O to C
  • Correct answer
    C
    the images C,B and A will shift towards O
  • D
    the images C,B and A will shift away from O

Solution

If d is the distance between slits and θ is the angle between 0th order maxima and nth order maxima, then for diffraction pattern dsinθ=nλ

Now, if the source is replaced by another source of shorter wavelength, then sinθ becomes smaller. Therefore, the angle of diffraction for all orders reduces due to which the pattern shrinks and images move towards the normal, not diffracted beam.

Hence, the images C,B and A will shift towards O

Hence, the correct answer is option: 'C'.

Relevant Questions