In Young's double-slit experiment, a thin sheet of refractive index 1.25 and thickness 0.5 cm is placed in path of the light from one of the sources. The path difference observed will be-

The correct answer is option 1) i.e. 1.25 mm.

CONCEPT:

• Young's double-slit experiment: It uses two coherent sources of light separated by a very small distance, usually, of the order of magnitude slightly greater than the wavelength of light used in the experiment.
  • It is used to study the wave nature of light.
• Coherent sources of light are the sources that emit lights of the same frequency and waveform and have a constant phase difference between them.
• Path difference: It is the difference in distance travelled by the two waves in reaching a particular point on the screen.
  • Path difference introduced by the sheet is given as;

δx = (μ-1)t

where μ = refractive index of the sheet and t = thickness of the sheet

CALCULATION:

Given that,

Refractive index of the sheet, μ = 1.25

The thickness of the sheet, t = 0.5 cm

Using

δx = (μ-1)t

⇒ δx = (1.25-1)0.5 cm

⇒ δx = (0.25) × 0.5 cm

⇒ δx = 0.125 cm or 1.25mm