Question

Which of the following is/are true for YDSE experiment?

• A. i, iii
• B. i, iv
• C. ii, iii
• D. ii, iv

Hint:

In YDSE, fringe width increases with the wavelength and decreases with the slit distance.

Answer 1

The Correct Option is B

Step 1: Understand the relation for fringe width in YDSE.
The fringe width \( \beta \) in Young's Double Slit Experiment (YDSE) is given by the formula: \[ \beta = \frac{\lambda D}{d}, \] where \( \lambda \) is the wavelength of light, \( D \) is the distance between the screen and the slits, and \( d \) is the distance between the slits. Step 2: Analyze the given options.
- (i) "Fringe width increases if slit distance is constant and wavelength increased." This is true because \( \beta \) is directly proportional to \( \lambda \), so if \( \lambda \) increases, the fringe width will increase. - (ii) "Fringe width increases if slit distance is constant and wavelength decreased." This is false because decreasing \( \lambda \) will decrease \( \beta \). - (iii) "Fringe width increases if slit distance is increased and wavelength constant." This is false because \( \beta \) is inversely proportional to \( d \). Increasing \( d \) will decrease the fringe width. - (iv) "Fringe width increases if slit distance is decreased and wavelength constant." This is true because decreasing \( d \) will increase \( \beta \). Final Answer: \[ \boxed{i, iv}. \]