Question 284: Wave Optics

Question

How is the interference pattern affected when violet light replaces sodium light?

Accepted Answer

In a two-slit interference experiment, the fringe width (the distance between adjacent bright fringes) is given by:
$$\Delta y = \frac{\lambda D}{d}$$
where:
$$\lambda$$ is the wavelength of light,
$$D$$ is the distance to the screen, and
$$d$$ is the distance between the slits.
Since violet light has a shorter wavelength than sodium light (typically, sodium light is around 589 nm while violet light is closer to 400 nm), replacing sodium light with violet light will reduce the value of $$\lambda$$.
Pausing the formula:
A smaller $$\lambda$$ means that $$\Delta y$$ decreases.
Hence, the fringes move closer together.
Therefore, the correct answer is:
Option C: Fringewidth decreases.

Answer

The fringes become brighter.

Answer

The fringes become faint.

Answer

Fringewidth decreases.

Answer

Fringewidth increases.

Wave Optics

How is the interference pattern affected when violet light replaces sodium light?

Choose the correct answer: