Question

In Young's double slit experiment, if the source of light changes from orange to blue then:

• A. the intensity of the minima will increase.
• B. the distance between consecutive fringes will increase.
• C. the distance between consecutive fringes will decrease.
• D. the central bright fringe will become a dark fringe.

Hint:

Memorize the visible spectrum order (VIBGYOR) and how wavelength changes across it. Wavelength increases from Violet to Red. This is crucial for problems involving color changes in optics.

Answer 1

The Correct Option is C

The fringe width ($\beta$), which represents the distance between consecutive bright or dark fringes in Young's double-slit experiment, is given by the formula:
$\beta = \frac{\lambda D}{d}$
Here, $\lambda$ is the wavelength of light, D is the distance between the slits and the screen, and d is the separation between the slits.
The fringe width $\beta$ is directly proportional to the wavelength $\lambda$ ($\beta \propto \lambda$).
The visible light spectrum, in order of increasing wavelength, is Violet, Indigo, Blue, Green, Yellow, Orange, Red (VIBGYOR).
This means the wavelength of blue light ($\lambda_{blue}$) is shorter than the wavelength of orange light ($\lambda_{orange}$).
$\lambda_{blue}<\lambda_{orange}$
When the light source is changed from orange to blue, the wavelength $\lambda$ decreases.
Since $\beta$ is directly proportional to $\lambda$, the fringe width will also decrease.
Therefore, the distance between consecutive fringes will decrease.