# A-level Physics (Advancing Physics)/Young's Slits/Worked Solutions

**1. A 2-slit experiment is set up in which the slits are 0.03 m apart. A bright fringe is observed at an angle 10° from the normal. What sort of electromagnetic radiation was being used?**

So, microwaves were being used.

**2. Light, with a wavelength of 500 nm, is shone through 2 slits, which are 0.05 m apart. What are the angles to the normal of the first three dark fringes?**

, where n is an odd integer.

Then, substitute in n = 1,3 and 5 to gain corresponding values of θ:

n |
θ (°) |
---|---|

1 |
2.9 x 10^{−4} |

3 |
8.6 x 10^{−4} |

5 |
1.4 x 10^{−3} |

**3. Some X-rays, with wavelength 1 nm, are shone through a diffraction grating in which the slits are 50 μm apart. A screen is placed 1.5 m from the grating. How far are the first three light fringes from the point at which the normal intercepts the screen?**

, where n is an integer.

Then, substitute in n = 1,2 and 3 to gain corresponding values of x:

n |
x (m) |
---|---|

1 |
30 x 10^{−6} |

2 |
60 x 10^{−6} |

3 |
90 x 10^{−6} |