# Worksheet: Diffraction of Light Waves

In this worksheet, we will practice describing interference patterns produced by waves that travel different distances and are diffracted by passing through gaps.

Q1:

Which of the following conditions results in the largest diffraction angle when a wave passes through a gap?

• AThe gap’s width is equal to the amplitude of the wave.
• BThe gap’s width is equal to the speed of the wave multiplied by the periodic time of the wave.
• CThe gap’s width is equal to the speed of the wave multiplied by the frequency of the wave.
• DThe gap’s width is equal to the speed of the wave multiplied by the amplitude of the wave.
• EThe gap’s width is equal to the wavelength of the wave.

Q2:

Which of the following is a correct definition of diffraction?

• ADiffraction is the change in direction of a wave that passes close to an object and changes its direction by an angle greater than 90 degrees.
• BDiffraction is the change in wavelength of a wave that passes through an aperture.
• CDiffraction is the change in direction of a wave that passes close to an object and changes its direction by an angle smaller than 90 degrees.
• DDiffraction is the change in speed of a wave that passes through an aperture.
• EDiffraction is the change in direction of a wave that passes from one medium into another with a different density.

Q3:

The diagram shows the wave fronts of two waves that have been diffracted through equally narrow gaps. Both waves have the same speed, wavelength, frequency, and initial displacement as each other.

How many wavelengths of this light is the left-hand gap from point ?

How many wavelengths of this light is the right-hand gap from point ?

Is the interference between the two light waves at point constructive or destructive?

• AConstructive
• BDestructive

How many wavelengths of this light is the left-hand gap from point ?

How many wavelengths of this light is the right-hand gap from point ?

Is the interference between the two light waves at point constructive or destructive?

• AConstructive
• BDestructive

How many wavelengths of this light is the left-hand gap from point ?

How many wavelengths of this light is the right-hand gap from point ?

Is the interference between the two light waves at point constructive or destructive?

• BConstructive

How many wavelengths of this light is the left-hand gap from point ?

How many wavelengths of this light is the right-hand gap from point ?

Is the interference between the two light waves at point constructive or destructive?

• AConstructive
• BDestructive

Q4:

Which of the following statements most correctly describes the relationship between the number of nearby gaps that waves pass through and the diffraction pattern produced by the waves?

• AA diffraction pattern is only produced if there are two gaps.
• BA diffraction pattern is only produced if there is one gap.
• CA diffraction pattern is produced by any number of gaps.
• DA diffraction pattern is only produced by a number of gaps equal to the wavelength of the waves.

Q5:

Which of the following statements most correctly describes the effect of white light passing through a gap about 550 nanometers wide?

• AThe different colors in the white light are diffracted by different amounts.
• BThe white light is not diffracted.
• CSome of the colors in the white light interfere destructively and are not seen in the diffraction pattern.
• DThe different colors in the white light are diffracted equally.

Q6:

Which of the following statements most correctly describes the relationship between interference of waves and diffraction of waves?

• AThere is no relationship between interference of waves and diffraction.
• BDiffraction occurs because of destructive interference of waves.
• CDiffraction occurs because of both constructive and destructive interference of waves.
• DDiffraction occurs because of constructive interference of waves.

Q7:

Which of the following statements most correctly describes how the wavelength of diffracted waves relates to the width of the gap that they pass through?

• AWaves are diffracted most strongly when their wavelength is equal to half the width of the gap that they pass through.
• BWaves are diffracted most strongly when their wavelength is equal to double the width of the gap that they pass through.
• CWaves are diffracted most strongly when their wavelength is equal to the width of the gap that they pass through.
• DWaves are diffracted most strongly when their wavelength is equal to the square root of the width of the gap that they pass through.

Q8:

Which of the following statements most correctly describes the result of waves passing through a single gap that is approximately the same width as the wavelength of the waves that pass through it?

• ANo diffraction pattern is generated because waves only pass through a single gap and there are no other waves for them to interfere with.
• BThe waves are diffracted from either side of the gap and the waves from each side interfere with each other, but no diffraction pattern is generated because these waves are all in phase with each other.
• CA diffraction pattern is generated because the waves are diffracted from either side of the gap and the waves from each side interfere with each other.
• DA diffraction pattern is generated because waves that pass through the gap interfere with other waves that pass through the gap after them.

Q9:

Light passes through gaps in a screen, A, B, and C, as shown in the diagram. The light passing through each gap falls onto the screen perpendicularly. The wavelength of the light through each of the gaps is the same but the gaps are of different widths. The light passing through each gap is diffracted. After moving a distance past the gaps, the wave fronts of the waves one wavelength apart are shown. The lengths of the leading wave fronts , , and vary depending on the size of the gap that the light passed through.

Which of the gaps is the nearest in width to the wavelength of the light passing through it?

• AGap C
• BGap A
• CNone of these patterns
• DGap B

Which of the gaps has the greatest width compared to the wavelength of the light passing through it?

• AGap B
• BNone of these patterns
• CGap A
• DGap C

Which of the gaps has the smallest width compared to the wavelength of the light passing through it?

• AGap A
• BGap C
• CNone of these patterns
• DGap B

Q10:

A light source emits light that passes through two narrow slits and then falls onto a screen, as shown in the diagram. Which of the four patterns on the screens (A), (B), (C), and (D) most correctly shows the pattern that would be produced on the screen by the light diffracted through the slits?

• A(A)
• B(B)
• C(D)
• D(C)