# Worksheet: Double-Slit Diffraction

In this worksheet, we will practice calculating the characteristics of an interference pattern made by the diffraction of visible light through two slits.

**Q1: **

A double slit produces a diffraction pattern that is a combination of single- and double-slit interference, where the first minimum of the single-slit pattern falls on the fifth maximum of the double-slit pattern. Find the ratio of the width of the slits to the distance between the slits.

- A 0.500 : 1
- B 0.250 : 1
- C 0.707 : 1
- D 0.200 : 1
- E 1.00 : 1

**Q2: **

When monochromatic light of wavelength 430 nm is incident on a double slit of slit separation 5 μm, there are 11 interference fringes in its central maximum. How many interference fringes will be in the central maximum of light of wavelength 632.8 nm for the same double slit?

**Q3: **

White light falls on two narrow slits separated by 0.40 mm. The interference pattern is observed on a screen 3.0 m away.

What is the separation between the first maxima for red light and violet light ?

At what point nearest the central maximum will a maximum for yellow light coincide with a maximum for violet light ?

What orders of maxima of yellow light and violet light will coincide nearest the central maximum?

- Ayellow order 3 and violet order 5
- Byellow order 2 and violet order 4
- Cyellow order 2 and violet order 3
- Dyellow order 3 and violet order 4
- Eyellow order 2 and violet order 5

**Q4: **

The first-order maximum for monochromatic light falling on a double slit is at an angle of .

At what angle is the second-order maximum?

What is the angle of the first minimum?

What is the highest-order maximum possible?

**Q5: **

Light of wavelength 720 nm is diffracted and the diffraction pattern produces a second-order maximum. What is the smallest separation between two slits that can produce this pattern?

**Q6: **

Find the distance between two slits that produces the first minimum for 410-nm violet light at an angle of .

**Q7: **

If both 500-nm light and 650-nm light each pass through two slits that are separated by 0.50 mm, how far apart are the second order maxima for these two wavelengths on a screen 2.0 m away?

**Q8: **

600 nm wavelength light diffracts through two slits separated by 0.12 mm.

What is the angular position of the first maximum?

What is the angular position of the third maximum?

**Q9: **

Two slits are separated by a distance exactly five times the width of the slits. How many interference fringes lie in the central peak of the diffraction pattern?

**Q10: **

A monochromatic light of wavelength 590 nm is incident on two slits with a width of 3.2 μm each. A diffraction pattern is produced containing nine interference peaks inside the diffraction pattern central maximum. Find the separation of the slits.

**Q11: **

Young’s double-slit experiment is performed under water of refractive index 1.33. The light source is a He-Ne laser of in a vacuum.

What is the wavelength of this light in water?

What is the angle for the fifth-order maximum for two slits separated by 0.32 mm?

**Q12: **

The central diffraction peak of a double-slit interference pattern contains exactly seven peaks. What is the ratio of the slit separation to the slit width?