Finite-Slit Diffraction and Double-Slit Fringe Intensities

All flashcards

What is the two-slit diffraction pattern?

It is the two-source interference pattern shaped in intensity by the diffraction pattern of each finite-width slit.

What does $d$ represent in $d\sin\theta=n\lambda$?

$d$ is the separation between the centers of the two slits; it helps determine the positions of interference fringes.

What is the role of the diffraction envelope?

It sets how strong the interference fringes are at different angles, even though the interference condition determines their approximate positions.

What is a missing order?

It is an interference maximum that is absent because it occurs at the angle of a diffraction minimum.

What condition gives single-slit diffraction minima?

The minima satisfy $a\sin\theta=p\lambda$, where $a$ is slit width and $p$ is a nonzero integer.

Quiz questions

1. Which condition gives the approximate angular positions of bright fringes in a double-slit pattern?Answer: $d\sin\theta=n\lambda$
2. What effect does finite slit width have in a double-slit experiment?Answer: It produces diffraction that modulates fringe intensities.
3. Which condition describes a single-slit diffraction minimum?Answer: $a\sin\theta=p\lambda$, with nonzero integer $p$
4. When is an interference order missing from a double-slit pattern?Answer: When its maximum coincides with a single-slit diffraction minimum.
5. For slit separation $d$ and slit width $a$ with $d/a=3$, which positive interference order coincides with the first diffraction minimum?Answer: $n=3$