[填空题]
Light with a wavelength of $750\,nm$ is incident on a single slit. The slit width $b$ is comparable to the wavelength of the incident light.
1.State what is meant by diffraction.
2.(1)On the diagram; sketch the wavefronts after passing through the slit.
(2)Describe the pattern observed on the screen.
(3)The slit width is slowly increased until it is much wider than the wavelength. Explain the effect on the observed pattern.
3.The single slit is now replaced with a pair of slits of spacing $d$ as shown.
(1)Describe the pattern observed on the screen.
(2)Knowing that
Distance between the slits $d=150\,μm$
Distance between the double slit and the screen $D=2.3\,m$
Calculate the distance between the centers of two bright fringes. s = m
(3)Explain how the widths of the slits will affect the appearance of the pattern on the screen.
